YC is a sort of incubator. YC news is what you've cloned. There are a bunch of open source things like that already. I wouldn't work on it myself - the important thing in these things is the community, not so much the technology.
I'm doing it just for fun. There is also bunch of programming frameworks and new frameworks are still appearing, so there is no reason not to do something just because there are some "things" which exist already :)
