[pemulis]

My advice would be to focus really hard on a single area in the market. Google (or the Asian companies you seem to be really talking about, like Renren and Sina) can copy your user interface and quote-unquote "idea", but their size creates problems. They're not as focused as a small start-up can be. Big companies lumber, small companies sprint.

Since all of the front-end parts of a website are stealable, you have to win by focusing on back-end technology and community. That's how all of the sites on your list have found success. For Quora, StackOverflow, and Wikipedia, it's the community. For eBay and Amazon, it's the back-end technology. That's somewhat oversimplified, but you get the idea.