Hoping on the social networking bandwagon is a terrible idea right now.
Think of it like the housing market, and right now it's completely over - inflated. In a couple months to a year, the bubble will burst and people will congregate back to the 2-3 largest sites around at the time.
You'll loose a lot of money on web hosting, not to mention the price to buy the code.
Speaking of which, why don't you just rip it from the site itself? :S
The only way to make this worth while is if you have a really good idea for a niche site, and a way to get word out fast so as to dominate the market.