From a Microsoft ad featuring Xerox:
Their largest application runs on new SQL Server™ 2005 64-bit running on Windows Server™ 2003, which provides 99.999% uptime.*But what's that asterisk? Looking at the small print at the bottom of the ad reveals "*Results not typical." Guess we're now well-set in a world where you can claim anything as long as it is disclaimed properly.
Copyright ©2000-2008 Jeremy Mooney (jeremy-at-qux-dot-net)
At least they were partially up front, the classic disclaimer where I work is to put the phrase "your mileage may vary" in all the emails where you mention any hard numbers. Granted, this is only for other engineers but still, same idea.