I also like this idea but I agree it has problems. Some of its problems might be quite serious. Does it become a binding contract? Who is responsible if the code doesn't work? Who owns the code? What happens if more than one person implements a solution? How should large projects be handled? Etc. Etc. Etc.
Really, someone could post a question like
I need a small script that does such-and-such. If a suitable solution is freely available, please point me at it. If not, I promise to make a PayPal donation to the PerlFoundation in the amount of $XX.00 if someone writes one for me. Any takers?
and they'd probably get help. The more I think about it, the more I think a separate section for this kind of thing might not really fit in here. Perhaps we could just let people know on a case by case basis that someone might help if they offered to make a donation...
"My two cents aren't worth a dime.";