That's the thing - there are a tonne of rent-a-coder clones, but I have a feeling the quality of coders on YC News is much higher than that of rent-a-coder. The problem is, if you start listing jobs here, people will come for the jobs, possibly bringing the quality down.
Perhaps limiting it to LISP, Haskell and Python jobs would work. Most of these sites target Java or PHP or Rails developers, so it's hard to find work in other languages.
even better, limit the ability for the job postings to even be viewed to only people with X karma. that would keep both the gig postings and respondents to people within the community.
(i've seen it done elsewhere with reasonable success)
I dont think karma is related to coding ability. There are plenty of smart developers who simply dont waste time posting or commenting, whilst those with higher karma might have high karma because they are unproductive
but the idea is good, if you can keep the hacker's quality up