Quick, someone go back in time to 2000 and try to convince the first human you find that this would really happen in a decade or so:

Microsoft plans to file a formal antitrust complaint on Thursday in Brussels against Google, its first against another company. Microsoft hopes that the action may prod officials in Europe to take action and that the evidence gathered may also lead officials in the United States to do the same.

Here's a Senior Vice President at Microsoft explaining the action:

At Microsoft we’ve shown that we’re prepared to work hard and invest literally billions of dollars annually to offer Bing, a search service that many now regard as the most innovative available. But, hard work and innovation need a fair and competitive marketplace in which to thrive, and twice the Department of Justice has intervened to thwart Google’s unlawful conduct from impeding fair competition. In 2008 the DOJ moved to file suit against Google for its unlawful attempt to tie up and set search advertising prices at Yahoo!, causing Google to back down. And last year the DOJ formally objected to Google’s efforts to monopolize book content, a position affirmed by a federal district court in New York just last week. Unfortunately, even this has not stopped the spread by Google of new and disconcerting practices in the United States.

Meanwhile, it looks like Google is trying to lock down control over their Android mobile OS. One of Android's early selling points was its openness. Gruber at Daring Fireball is calling this a bait-and-switch.