After Microsoft bought Lionhead, it seems that the Redmond giant is after another firm.

In a deal estimated to $200-400 million, Microsoft is after Massive Inc. This move signals that fact that Microsoft is expanding rapidly, especially the in-game advertising.

It seems that the deal was not announced and Microsoft is using the policy “no comment”, but we heard a little rumor according to which the deal will be sealed next week.

With approximately 80 staff and a number of top publishers signed to its in-game advertising network, including the new Acclaim Games and Take-Two, Microsoft sure takes a big piece of the pie with this acquisition.

Another of Massive’s partners is Sony Online Entertainment, and it is unknown at present how the acquisition deal will affect that relationship, although it’s possible that Sony could also step into the game with an acquisition of one of Massive’s competitors in the market, such as Double Fusion.

We also heard that Microsoft’s acquisition is part of a much wider strategy tied to online gaming and entertainment, eventually linking Massive’s ad network with its own ad-brokering service, AdCenter, which will provide a similar service to Google by linking online ads to search results. This could be done to Xbox 360 titles so the plan seems to be bigger then we expected.

We will keep an eye on this.