Good questions paul -
There have been $10 LE's and even $20 LE's from Atlantic City. If you had asked me this at the end of last year I would have said that the $5's are slowly reducing and the $25's are increasing (no empirical evidence, just my point of view).

Atlantic City has no live $10 chips (there is at least one $10 house chip that never put into play AFAIK) so 99% of all the $10 chips are LE's. Yes you can bet them at the tables - well after you prove to the dealer that they are a real chip :) but they are really made for collectors.

This year, AC (with the Plaza and Tropicana leading the way) have quite a few $5 LE's and it seems that there are more coming before the end of the year. So hopefully it will continue on. I'd rather collect $5 LE than $25. Its cheaper for me, easier to get (cause they usually make more) and easier to trade for other chips from other areas.