i am sure this is a simplification of the situation, but it still is interesting to ask yourself why exactly microsoft feels compelled to release IE8. from the very beginning, IE was a tool to establish or maintain market dominance. it started with the idea of wiping out netscape, and then went on to try to establish ActiveX as a
part of the web. the idea was that even though the web might have some advantages, it should still be sufficiently lock-in so that companies can make sure their products are required.
adobe's Flash probably had the biggest success in that field for the past years, becoming the de-facto standard for multimedia content (since the W3C basically forgot that multimedia even existed and only recently decided to at least try to establish some standards for this area). looking at adobe made microsoft envious, so after a really long time they now finally decided to launch the plug-in war.
the marketing power behind Silverlight is much bigger than anything adobe could ever dream of, so expect more not-so-subtle attempts to push Silverlight such as microsoft's new download page or the NBC olympics coverage. even though admittedly for the olympics (or any other multimedia-centered site) some plug-in is required due to the lack of actual standards for web-based multimedia...
but the important issue is that microsoft's attempt to push Silverlight could do much bigger harm to the web than adobe could ever do. adobe is still pretty successful in convincing multimedia people that by developing Flash apps, they are actually developing next-generation web content. microsoft with its far bigger marketing muscle and many more developers behind it will be able to get many more people to believe that they are developing web apps and designing web content, while in fact all they do is writing proprietary apps and designing proprietary content which are distributed over the web.
the more i write about these things, the more i see many parallels to the REST vs. SOAP debate. REST is about designing apps in the web-style way, whereas SOAP is about writing apps that use the web as a transport infrastructure. the same can be said about web content and Flash/Silverlight: the latter are simply using the web as a transport infrastructure. we'll see how far microsoft is willing and able to go with that, but it's just sad to see that now that the time of Flash seems to be finally coming to an end, the next thing is popping up.