The way I see it is this. Silverlight is a killer application in terms of streaming media, especially media that is paid for to TV's and other media devices like media enabled computers because it solves the one intolerable thing which is hitching and stuttering streams. Natal links into this because its not just a gaming interface, but its also a multimedia interface so look to TVs integrating the Natal interface by the end of next year. I've already seen a demo of one so this has likely already been set in motion. The streaming music service is just as important to this as it is to the Zune and Xbox 360/PC.
Microsoft office online is there for two reasons. Its to counter Google apps and Open Office by providing an essentially free legitimate office version. Since most people understand that they need to use Office, they will probably get quite high takeup of this service to the expense of Google and Open Office since thats what companies use. Since companies know that everyone can use Office they stick with that platform because training is more costly than buying Office. Its a vicious cycle which keeps Microsoft in power here.
The second reason is to bolster the Live login/online system. Microsoft essentially wants to turn Windows Live into their next monopoly for universal online passports. What this means is that once you log into Windows you've essentially logged into all your favourite sites/MSN etc at the same time. What they probably want is everyone who has Windows to use Windows Live as their passcard for the internet and that passcard will include all their DRM etc in the one place. Essentially they want to solve the DRM hassles and house all the media purchases under their roof and solve the final problem thats holding back adoption of web content. You get less hassle, they get $$$ its a fair trade though its probably enough to put the regulators into a panic.
Tease.
