Google has acquired internet security provider Postini of San Carlos, California, for $625 million. The sale represents an exit for a host of VCs, who in total invested $36 million: AltoTech Ventures, August Capital, Bessemer Venture Partners, Mobius Venture Capital, Pacifica Fund, Summit Partners, and Sun Microsystems. Summit Partners has been a Postini investor since 2001. www.postini.com