By Gerry Shih SAN FRANCISCO (Reuters) – Alibaba Group Holding Ltd may be making its debut on Wall Street later this summer, but its certainly no stranger to the investors of Silicon Valley. In the past 18 months, the Chinese e-commerce giant has burrowed its way into the Valleys exclusive investment circles, snapping up sizeable stakes and board seats in fast-growing startups that could provide strategic advantages for when, not if, the company challenges Amazon.com Inc or eBay Inc on their home turf. A U.S. investment team headed by cable magnate John Malones former dealmaker, Michael Zeisser, targets stakes in e-commerce, mobile and logistics-focused companies which combine online and offline operations, people familiar with the U.S. operations said. Alibabas vision for the worlds largest consumer market has been the subject of intense industry speculation.