Imagine there was one number that could sum up how influential you are. It would take into account all manner of things, from how many people you know to how frequently you talk with them to how strongly they value your opinion. Your score could be compared with that of pretty much anyone in the world.

Maybe it’ll be called your Google number. Google (GOOG) has a patent pending on technology for ranking the most influential people on social networking sites like MySpace (NWS) and Facebook. In a creative twist, Google is applying the same approach to social networks it has used to dominate the online search business. If this works, it may finally make ads on social networks relevant—and profitable.

Google declined to discuss its idea with BusinessWeek. But it is based on the same principle as PageRank, Google’s algorithm for determining which Web sites appear in a list of search results. The new technology could track not just how many friends you have on Facebook but how many friends your friends have. Well-connected chums make you particularly influential. The tracking system also would follow how frequently people post things on each other’s sites. It could even rate how successful somebody is in getting friends to read a news story or watch a video clip, according to people familiar with the patent filing. “[Google] search displays Web pages with the highest influence—it makes complete sense for them to extend this to online communities and people,” says Jeremiah Owyang, an analyst at Forrester Research (FORR).

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