The husband and wife team who started Snopes are admittedly very liberal. I know a couple things they claim are legend which are true (can't remember the details but they were about Hitlery). Snopes just get their info from the internet, as we all do!
They are right sometimes no doubt, but certainly not infallible, and they do have a strong liberal bias.
The UPS uniform hoax has been around a very long time. I have seen it come up quite a few times. Lots of info on Google about it:
http://www.google.com/search?hl=en&ie=UTF-8&q=ups+uniform+hoax&btnG=Google+Search
Thanks for the info about the Snopes site.