Bill,
The official party line is that you should clean your diffusers regularly to avoid this, and I agree with this. In reality, I am probably one of the worst at cleaning my diffusers. I've had GLA's inlines for about two years, and have probably only cleaned them 3 times. They still work fine despite this. Take what you will from the anecdote, but I think that some diffusers are just more blockage prone than others, which may play into the choice of what to get for some.
Of course, atomizers are operating at 30 psi or more, so aquarium gunk would be hard pressed to block it compared to simple ceramic filters, which may be playing into it.