Google acquisition last month of Postini for about US$625 million was not actually a big surprise given, which the companies now have had a working relationship for the last few months for the former to offer the latter with security services.
The more visible reason for Google Postini is that Google desires to boost up its Apps offering so that it could race more successfully with Microsoft Office and travel users of the latter to the online/offline Google offering, principally in the enterprise space. Postini might surely assist Google to do that by providing healthy security, archiving and other capabilities, as well as by sending a huge number of potential customers for Google Apps.