Even thought it says “more than 1,000 small businesses” sign up for Google Apps every day, the search company wants more. It wants big business. It wants corporations with thousands of employees and millions of pages of indexable information.

There’s only one problem: big business doesn’t always play the same way small business does. In particular, large corporations are bound by rules, regulations, and internal red tape that make it more difficult for them to join Google’s computing cloud.

In an effort to make it easier for larger companies to use Google Apps, Mountain View has announced its acquisition of Postini - a company that deals in securing, managing, and archiving digital mediums (email, instant messages, etc):

Google Inc. announced today that it has signed a definitive agreement to acquire Postini, a global leader in on-demand communications security and compliance solutions serving more than 35,000 businesses and 10 million users worldwide. Postini’s services — which include message security, archiving, encryption, and policy enforcement — can be used to protect a company’s email, instant messaging, and other web-based communications.

The deal, worth $625 million in cash, is designed to bring more control over access and archiving of Google Apps data to bigger corporate customers. I have no doubt that Google will adapt the technology to also handle Docs & Spreadsheets data as well.

More information can be found in the official press release, Google Blog post, and Techmeme.