Adding a bit more to my earlier post:
Here's a discussion (elsewhere) where someone describes how they have used Corn Flakes in their beer: http://hbd.org/brewsandviews/messages/20001/20109.html?1074488172
I looked up the ingredients for Kellogg's Corn Flakes. It's got corn, sugar, malt flavor, and some salt. Since all of those except the salt are pretty standard beer adjuncts, I don't think there'd be any major problems assuming their processing/cooking sufficiently gelatinizes the corn. So it's probably a lot closer than Cheerios to oats, but still not a substitution.
edit: I see m_stodd posted the ingredients link above my post...