Google's fourth and most ambitious attempt at social networking has set Silicon Valley abuzz, with membership soaring past 10 million people in just three weeks. Vic Gundotra and Bradley Horowitz, the two executives in charge of Google+, said in an extended interview that they closely studied Google's previous failures with Orkut, Wave and Buzz to find a better approach. They also found a close-knit team of engineers and designers willing to take a risk.