Lanefan
Victoria Rules
Yes you are! Today's my day to be pemerton...I'm not Lanefan

We pass notes and occasionally set up elaborate schemes; but much of the time it is, as you say, frontstabbing.but where there has been PvP in my games it has normally been with consent by both players - ie an understanding that they are happy to play out the conflict between their PCs - or at least with a fairly light-hearted attitude.
And it case that doesn't make it clear - PvP in my game has always been out in the open as far as the players are concerned, even if the PCs don't always know what's going on. So the backstabbing, if any, is only a part of the fiction - at the table itself there is only frontstabbing!
And talk about players carrying the story! When they're at each other's throats I don't have to do a thing except adjudicate the occasional rule or spell effect (or rewrite and pass on notes, if required)...I can sit back, crack a beer, and enjoy the entertainment!
In character, I once had an entire adventure designed for me by another player so I could get back the +2 Sword of Healing (which I'd stolen in the first place; and its previous owner had stolen it also) she had stolen from me. That one sword was in fact stolen somewhere over a dozen different times by about 7 different people; I wound up with it in the end, and only when I had loaned it to someone - i.e. it changed hands without being stolen - did it finally meet its demise. (it was last seen in the throne room of Hel's palace, if anyone ever wants to go get it)
Lanefan