I'm surprised that I haven't hit this before at Microsoft, but I actually hit an OOF infinite loop today.
For those who don't know, "OOF" is an acronym that refers to someone being out of the office. The Exchange team gives a nice run-down on the history the term here.
When people are out of the office, it's common to set up an auto-reply e-mail message providing contact information, and these messages often refer the sender to someone else for urgent issues. By now, you've probably guessed what an OOF infinite loop is: person A has an auto-reply OOF message that says to contact person B, and person B has an auto-reply OOF message that says to contact person A.
Of course, it doesn't have to be that simple. There really is no limit to the number of people who can be involved in one of these infinite loops. Which gives me an idea for what to do right after we ship Mac Office...
Currently Playing in iTunes: Will it Go Round in Circles by Billy Preston