This week, Microsoft Corp. (NASDAQ: MSFT) announced that it was bumping the amount of storage for its freely available Windows Live Mail from two gigabytes to four gigabytes. Yahoo!, Inc. (NASDAQ: YHOO) bumped its free email storage limits from two gigabytes to unlimited storage earlier this year. What has Google, Inc. (NASDAQ: GOOG) done in response? Well, the internet search giant has kept its free email storage level at 2.8 gigabytes, but it wants customers to pony up some cash for an upgrade.

Google will give its Gmail email users another six gigabytes of online storage for an additional $20 per year when its competitors are giving away more gigabytes for free. For a company known for giving away almost everything and making up revenues with highly successful advertising, this is sort of a surprise. Want even more storage from Google? The company will charge you $75 a year for 25 additional gigabytes and even let you have 250 gigabytes for $500 per year. At Yahoo! mail, by comparison, unlimited storage is still free. However, Yahoo! has checks built into its system to ensure that space is for large emails, not simply online file storage.

Is Google not making enough from ads automatically inserted into its Gmail offering and therefore wants to now charge customers who are heavy users of its email service? It sure appears that way, but maybe the company is just trying to get paying subscribers in its ranks instead of giving away everything for free and hoping that its advertising model doesn't ever slow down in terms of revenue growth. Even though it sounds like I am down on Google here, I applaud the company for making an effort to glean revenue from more than just one source -- those text ads that appear next to Google searches and Gmail email messages.