Everyone at our playgroup has been giving the kids popcorn since about 1 years old.
When I mentioned that it was on the list of most chokable foods the moms were stunned..... and continued to feed the kids popcorn.
here's a link to dr Sears' chokable food pagehttp://askdrsears.com/html/3/t030400.asp
HE doesn't specify there or in his baby book (goes to age two) about at what age popcorn is safe to give. He DOES specify at both the site and in the book that it is "popcorn kernals" which are on the list... I don't know if that is unpopped kernals or all parts of the kernal. Certainly I have gotten a popcorn kernal in my throat at times in my life but it has never been life threatening even as it sucked at the time. I guess each mom has got to weigh the potential risk for their own child in terms of age, ability, desire, and potential consequences.
DD is almost 2 and she loves popcorn... I take out all the unpopped kernals and only let her have one at a time, in my presence. I am exceedingly careful about what I give dd in terms of chokability, so maybe I'll just discourage the popcorn for a bit. We'll see.