There are definitely a lot of successful startups that take an idea from one country and do it in another. Sure, they may not be huge, but might make some good money in any case.
Yes, I also thought about XING (http://www.xing.com) here in Germany. Many people say it's just a copycat of LinkedIn, but in my opinion they have created a much better business network than LinkedIn. And: they're profitable. Their business model ("Freemium") worked out and they've sucessfully expanded in other European countries and China.
I may be working on a similar business network here in the US (as a contract Rails coder), but with features tailored to a specific market. Even though I'm just doing this as a contract gig (no equity), I genuinely think they will succeed. They are tightly focused on a market that is willing to spend money, can get some good initial traction through personal contacts, and the market they are going after needs features not present in 'generic' sites like LinkedIn or Facebook.