Microsoft can now officially feel yet more threatened: Google has released a beta version of Chrome, its new browser. A harbinger of things to be is this text from their "Why?" page:
[...] We also built V8, a more powerful JavaScript engine, to power the next generation of web applications that aren't even possible in today's browsers.

This is just the beginning - Google Chrome is far from done. [...]
Microsoft has two vast revenue streams: Windows, and Office. Google already has web-based competition for Office, but online applications are still severely hampered by the capabilities of today's browsers. For now, this has tilted the playing field in favor of traditional applications that install on the user's machine, providing superior functionality.

But if Google's browser gets widespread adoption, it appears certain to lead the way into support for more advanced browser features which will allow online web applications to become more capable of competing with their desktop counterparts. And at some point in the next few years, you will find yourself at a computer that doesn't have Office installed, you will need to perform a spreadsheet computation, and you will find yourself considering:

Do I (A) go to the store and pay $400 for MS Office? Or do I (B) go to OpenOffice.org, and wait while I download a huge installer? Or do I (C) just surf to Google.com, and use an online spreadsheet that immediately works?

Considering also that, in option (C), your data is stored on the net, can be accessed any time from anywhere, and is automatically backed up?

More and more people will find themselves choosing (C) over the previous two options, until eventually, option (C) will make such obvious sense that Microsoft's Office revenue will drop right through the floor.

That's 50% of Microsoft's revenue being threatened right there. Can the desktop eventually become so unimportant that Microsoft's Windows revenue will also be threatened? Maybe.

Disclaimer: Since me and my company depend on developing SSH software for Windows, it is certainly in my best interest for Windows to remain very healthy for a very long time. That doesn't mean it's going to happen, though.