Because I've been involved in Tech Support at various levels for a number of years, I tend to use PEBKAC quite a lot, and I find that very few people know what it means. But that's probably a good thing, as I imagine there are a fair number of users that could take offense at being told "Ah, yes. I know your problem. Seen this many times before - a classic case of pebkacery" - if they actually knew what it meant ;)

I've also seen a few here at PM that I'd not previously seen elsewhere. YMMV is one example - and in fact, your post prompted me to look that one up right now ;)

Cheers,
Darren