All this does is statically link the user to the GitHub page. It does not actually "Watch" the repo when you hit Watch. While nice, it's just a glorified link. The counter is the only real feature here.
I really wish github would develop a web intents api like Twitter. Then one can watch repos and follow other users much like the follow bottons for twitter.
In that sense, HN is just a glorified forum. Actual value comes from the context. This is best available thing for now.