why? Im sure people would have made as good suggestions if the offer hadn't been made. Offering a (one assumes small) cut for creative input that could well heavily influence sales seems a nice gesture :)
I would have prefered a "copy" of the app, even though I don't own an iphone. Offering me equity for something trivial that I would have done for fun, for free, well .. just makes me feel both horrible. I don't want anybody to go through paperwork or calll up the lawyer or print me a stock certificate for $1 just because I suggested a name for the app.