Microsoft agreed to purchase in-game ad firm massive Incorporated, according to press reports. Massive can insert ads in real-time inside video games.

The sale is pegged at between $200 and $400 million.

And how large is that advertising market? In-game advertising is expected to grow to $732 million by 2010 -- up from $56 million at the end of 2005, according to a report released last week by the Yankee Group.