> Microsoft isn't a behemoth it used to be.
Microsoft Windows desktop market share: 90+%
Microsoft Office market share: 90+%
Internet Explorer market share: 40-50% (still by far the most popular browser)
> I think the only thing they have to show for themselves in last decade is Xbox. I can't think of any other new market where they have been as successful.
A few obvious examples:
Client division: Windows 7
Server and Tools division: Windows Server, Visual Studio, SQL Server, Exchange Server
Business division: Office
Entertainment and Devices division: XBox 360, various games, various mice/keyboards/etc.
R&D: Seems to employ/fund just about everyone doing industrial programming language research except for the 3 Google managed to hire, and a huge proportion of the industrial HCI research too.
MS obviously aren't dominant in all of these fields (compare Oracle for DB, the other major consoles for gaming, etc.). However, no start-up is going to compete with these sorts of products any time soon.
The most obvious targets for disruption by smaller players are the browser market, except that both Chrome and Firefox have basically written off business users as clients so MS will have a base there for as long as it wants one, and programming, except that with the resources and R&D Microsoft are throwing into that field lately it seems more likely that MS will pull away from the small time competition rather than losing ground for the foreseeable future.
That means at best, start-ups are going to be competing against Microsoft's secondary portfolio, things like BizTalk and Dynamics, and it's not as if there's a huge amount of innovation going on in the start-up sector in unsexy fields like that (unless you still think a business plan featuring the word "cloud" in big enough letters is worth VC funding, I suppose, but since the likes of Google Docs haven't even made a dent I don't suppose MS will be too worried about that sort of start-up for now).