I get to jam online on a couple of other guitar forums. I do have a guitarist buddy that I jam with but its more me giving him pointers rather than jamming.
I am a member of another forum guitarforum.com where there is a Jam section on the forum where fellow forumers upload a backing track for players to jam on and post their efforts, at the moment there is a focus on beginners and encouraging them to join in jamming.
Another forum I am on (the Fractal Audio forum) I have a couple of buddies (one lives in London near me and the other in Memphis USA) we pick a backing track to jam over, slice it up into 3 time slots and allocate to each player and then we each lay down our solos in our allotted slot and its a lot of fun.
No reason why something like that can't happen here if there were people up for it. Also, guitar is my secondary instrument, my main instrument is keyboards and I sometimes jam soloing on keyboard as well on other forums which is accepted by other guitarists lucky and I'm not booed off the pitch lol.