anemones should be left in the ocean where they can live their full lives (30 years??). That is way beyond the life of any tank that we have.
Too many of these creatures die due to poor lighting, poor water quality, overfeeding, underfeeding, etc. that the few that live 5+ years in a tank don't justify the trade.
Now for those who have had a reef tank for 5 years and already know how to keep very stable water parameters I may understand getting one and fragging it for sale/trade. At least that helps to leave the wild population intact. But until there is sufficient quantites of fragged anemones for sale, please think again about getting one. Clown fish don't need one. They move around and kill other corals trying to find a 'happy place'. They die all too soon and suddenly, though most waste away for a period of months till they show signs of it (at which point it's too late to help).