Microsoft has a nasty habit of allowing bizarre adverts into its messaging application, Windows Live Messenger. All ranting aside about the multi-billion-dollar corporation enlisting in-product ads, there doesn't seem to be a great quality control system in place.
First spelling mistakes, as I found last year:
Now crude and ambiguous links to what may possibly be a scat forum:
Thanks to Kamil K via Jake Vinson over at The Daily WTF for the heads-up on that last one.