You should've known it: Microsoft's Windows Genuine Advantage tool phones home daily and that fact isn't disclosed in the EULA. Read the article over at Seattle Post-Intelligencer, where it says:
"Microsoft Corp. acknowledged Wednesday that it needs to better inform users that its tool for determining whether a computer is running a pirated copy of Windows also quietly checks in daily with the software maker."
"Lauren Weinstein, who is co-founder of People for Internet Responsibility and was one of the first people to notice the daily communications to Microsoft, said he understands and sympathizes with Microsoft's desire to control widespread piracy of its flagship product. But he said it's problematic that Microsoft did not disclose all the tools' communications with the company."