According to an article on Groklaw, Microsoft is misrepresenting what the Windows Genuine Advantage (WGA) tool is to pressure people into installing it. It comes with no uninstall, it fails to disclose many pieces of information it provides to Microsoft, and it misrepresents itself as a 'critical update' when it does not address any security vulnerability, although it remains to be seen if it can create one.

ZDNet has a series of screenshots so that you can see exactly how badly it misrepresents itself. Oh, and it also checks for updates, so Microsoft can presumably execute arbitrary code on any machine with it installed, merely by making that code part of a WGA update.

Slashdot