I knew I was going to spark some debate but......
I would like to answer you all individually but I also have to work so there just isn't the time so I will try to respond to everyone in this reply.
As I mentioned in my original post, seeing a Betta being kept in a bowl in a pet store should not be considered a cruel act. Keeping a Betta in a container (of any size) of dirty water or with fast moving water is what's cruel. Today's Bettas are not like their foremothers and forefathers as they now have these unwielding fins that make it more difficult to swim with.
If any of you are old enough to remember the first delta tailed guppies, you'll recall that the bigger the tail got, the slower the fish swam. That's because the tail weighed the fish down. Many guppies were coming down with spinal problems because of the mutation. If you look at today's Guppies, the tails are not as big and the fish seem to swim easier. If you were to race a regular angelfish against a veiltail angelfish, the regular would win every time. That's because they have the original equipment that they evolved with which enables them to swim faster. Bettas are no different. They are the veitail angelfish of their specie. Beautiful to look at but not functionally sound.
Proper fish keeping requires us to understand the habits and habitats of the fish we keep and do our best to duplicate them in a controlled environment. In the case of a Betta, it's habitat when it was in it's original shape was a shallow often stagnent body of water. The size of the body of water was not really of significance because the fish did not use the entire body of water. It was not a migrating specie. It did not move from a winter home to a summer home. It did not go from shallow water in the heat of the days to deep water when the temp dropped (which it mostly didn't do.) In this scenario, the fishes ability to survive was because of the labrynth organ. It's that same organ that enables today's Bettas to be kept in Bowls with no filteration or water movement. That's the reason it can be done which cannot be distupted.
If you are not seeing good colors in your bowl kept Betta, you are not caring for them correctly. I have beautiful Bettas in bowls that blow nests all the time. The sure sign of a healthy fish is good color and wanting to breed. I acheive this in bowls all the time. If you are not, you are doing something wrong. That is not me talking, that's your fish talking to you. You need to change what you are doing. (Talvari, if your Bettas are not looking good at your store after a water change, you may need to check your water. You may be having excess chemicals in it that your systems with carbon are taking out so it's not effecting your other fish. You may also want to use bottled water and temp change on some to experiment if this solves the problem. The problem may also be with your supplier. They may just be giving you crappy fish.)
If you maintain this fish correctly, it can thrive in a bowl situation. Unlike the poster's argument about keeping an adult Oscar in a 10 gal tank, that fish will never thrive in that small amount of space. A betta can. The correct way of using a bowl takes a lot of work. If you are up to the challenge, there's no reason not to go for it. NOW, I'm not saying that you can keep Bettas in bowls and neglect them. That's cruel. It's just as cruel to put them in a tank and neglect them. As for longevity, today's Bettas don't seem to live as long as the ones I used to keep in the 1960s and 1970s. It most likely is due to all the inbreeding that has been down over the years so there is not much one can do about that. I once watched a documentary on PBS about health and in it, they talked about a Betta which was kept for 9 years in a laboratory. The experiment was to determine the body fat content between the fish in a bowl being fed beefheart and a fish in a tank being fed beefheart. I don't recall what the outcome was of the trial but I do remember in that piece that the fish that lived 9 years was on a regular routine of swimming around a 20 gal long tank. The reason it was swimming was because the scientist was chasing it!! EVERY DAY!!! When left alone in the tank, the fish primarily stayed in one area. Once again, just because the fish has the room to swim does not mean that it wants to swim.
Temp: A Betta CAN live in temps as cold as in the upper 50s and as high as the mid 90s. The best temps to keep them in is between 70 and 80 degrees. How you get the water to that temp, I'll leave up to you. I told you how I do it in my house. I use heaters in my Betta systems outside. The number is what's important, not the method you get that number
Breeding: For breeding Bettas, most books and breeders will tell you that Bettas breed best at about 80 degrees. They like the warmer water for breeding. That may also be why they look better in warmer water, they need to look their best to attract a female. I've had bettas breed in 90 degree water and 75 degree water. These spawns did not do as well as the ones bred around 80 degrees.
As for the setup for anabantids, the first time I came to FL and went to a fish farm, I saw stacks of styrofoam boxes with plastic full box bags in them and being the curious type that I was, I looked inside the boxes. Each box had a pair of gouramis in them. Each box had a floating plant and a bubble nest in it. No water movement, no airstones , no heaters. (Hey, it's Florida, who needs heaters? LOL) This was exactly how I was breeding gouramis in NJ except I was using a tank and not a box and I needed a heater because hey, it's NJ and it gets cold up there! LOL. The setup Hobgob is discribing is for the second stage of the growout for anabantids. In the case of bettas, Betta fry are sensitive to water movement so I doubt this was the setup at the spawning. If it was and the fry survived, good for you. It's the exception and not the rule. For my other fish, this setup is about accurate with small tweaks depending the specie I was breeding.
Finally, yes, those huge Tarpon are found in all types of water here in FL. There are some that have become landlocked in canals so they are freshwater Tarpon now. They can go into low oxygen level waters because they too have a labrynth type organ. The huge fish in South America have the same situation. When the Amazon river floods, these fish can get all the way up into the "back country" because there is water there. When the water receeds, some fish can get caught in some deeper "Puddles" where they have to survive until the next rainy season. If there is no water movement, how do they do that? Here's a hint, a labrynth type organ. The point I was making was that these huge fish would have the ability to live in a bowl if you had the right sized bowl. An Oscar, just for example, would never be able to live in a bowl without supplimental airation. The example of the neon tetra in the bowl was really a bit off course. It was being kept in a ecosystem and not just a bowl. It was being given supplimental airation via the plants and food from whatever the system was providing. That's much different than a fish, a bowl of water, and nothing else. There's nothing stopping you from putting a live plant in your bowl if you have the light to keep the plant alive. That's about as natural as it comes. It's also about as close to a Betta's natural habitat as there is. So you mean that anybody who is not keeping a Betta in a tank with live plants is being cruel to the fish? I would have to argue that point with my fish.
So I think I covered everything. You can agree or disagree with me all you want.
I have many years of experiences and training that gives me the ability to debate these issues. I even have some books that were so wrong when they were printed that I just laugh at these today. The best one is from a book on angelfish. There's a picture of a marble veiltail angelfish with a caption saying" Not too pretty, it is doubtful that the Marble variety will ever achieve popularity." You see? Books are good but experience is better. I loved my Marble Angelfish