Ali and Hadi Partovi may not be household names, but the twins have quietly helped launch some of Silicon Valley’s biggest startups of recent vintage. Hadi co-founded Tellme Networks, which Microsoft bought for a reported $800 million. Ali co-founded Internet advertising pioneer LinkExchange, which Microsoft bought for $265 million; he later became one of the first investors in Zappos, the online shoe retailer launched by LinkExchange co-founder Tony Hsieh. Amazon bought that one for about $850 million.