IMO, Sharepoint is Microsoft's next big thing. They are becoming indispensable to midsized and large companies and creating a foundation that helps them keep selling copy's of Windows, and Office while setting up yet another revenue stream. Granted selling to other companies seems to be what large organizations do when they die, but it's still a huge source of revenue with little real competition.
So, if you are building a web app you can probably ignore Microsoft, but if you are building an OS, or Office product there is still a huge shark swimming in those waters.
Some people like to complain about how companies end up depending on home-brewed Access and Excel applications. The IT guys didn't have the time/resources to do "a proper job" so the business workers just learned stuff on their own and wrote their own apps.
My suspicion is that Sharepoint and Infopath will be the next generation of home-brewed company apps. Companies already have them, so they don't need to be buying X, Y or Z to start writing apps to keep their company going.
I think focusing on selling to other companies is a difficult trap to get out of. After the first sale companies can be milked for an extended period for support contracts / upgrades. Innovation is not really needed and growth / profit are an easy to understand process. You can even make money by bribing middle managers (see: drug companies for an example of this).
However, individuals require far more bang for the buck. So the margins tend to be far smaller and you need to sell to large numbers of people constantly to keep up.
At the same time selling to companies tends to focus on boring products so most of your innovative people tend to leave. It's not exactly a binary choice, but companies like AT&T often go from selling to individuals, to making money from companies, to making money from the government. In the end the quality of your competition tends to drop the closer you are to working for the government which is why I think it's a death spiral. Overtime the company becomes unable to deal with change and the next round of innovative companies tend to disrupt them.
PS: Which is not to say old companies like GM can't sell products to customers it's just they stop being able to make much money doing so unless they can leverage a monopoly.
Aren't services like Sharepoint fundamentally inferior to "cloud computing" (for lack of a less buzzy phrase)? I've heard this for almost a decade, but isn't it about time people see local e-mail hosting like running your own generators instead of "trusting" an electric company for your electricity?
That's why Microsoft has two different levels of managed Sharepoint hosting: Office Live (very small businesses), and Microsoft Sharepoint Online (small or large businesses). Similarly, they have Microsoft Exchange Online, which is managed Exchange hosting. They are building caching infrastructure into Windows 7 so they can offer even Active Directory and file sharing as remote, managed services.
As far as I can tell, all of their server-side software is or will be offered in a Microsoft-hosted-and-managed configuration. And, it won't be trivial to switch back and forth, but it will at least be possible to do so.
Additionally, Microsoft seems to be working with Amazon Web Services since AWS supports Windows Server. If you don't want Microsoft to host your applications then you can do it yourself on AWS or on your own servers.
So, if you are building a web app you can probably ignore Microsoft, but if you are building an OS, or Office product there is still a huge shark swimming in those waters.