Valve's employees mention it in the Developer's Commentary. You should go listen to it sometime.
Edit:
Oh, I almost forgot. My copy of TF2 was wigging out tonight. When I went to switch weapons, nearly 1/3 of the time, it would immediately switch back to the weapon I just had. Same with switching disguises as Spy.
Has anyone else run into this, and if so, how did you fix it? Maybe it's just lost packets between me and the server, although that should be reflected in the ping time.
Edit 2:
I've deleted my local TF2 files and am reinstalling from Steam.