It's no secret that Google (NASDAQ: GOOG) is super-serious about its web applications business. Google Docs features a notebook, word processor and spreadsheet functions, which are all available for free over the web. Although the company continues to say that it is not looking to complete against Microsoft (NASDAQ: MSFT) Office, it is. Google just likes deflecting competitive talk until the products show what they can do.

To ensure that those web applications are as secure as possible, Google plans to buy Postini for $625 million. Postini offers a complete suite of security tools to help protect email, instant messaging and other web-based applications. Although focus on the Postini purchase has centered on Google needing to shore up its Gmail web-based email service, this acquisition underscores how Google is using its Web-based applications to gain customers of all sizes. Microsoft Office be damned.

Think about Google's collection of web-based applications now: Gmail, Calendar, Talk, Docs & Spreadsheets and Personal Start Page. That's quite a bit of web muscle Google flexes, and securing all those pieces from any threat would seem to be a main priority for the web search leader.

Remember, Google lives or dies by the web browser, since it produces no standalone software that brings in any revenue. Well, maybe a tiny amount from Google Earth, but that's about it.

The Postini acquisition is more important than its initial glance, although the purchase price seems a bit high. But, without web security, Google could wither on the viine. We can't have that!