Been doing it for probably 5 years now. Never any problems. I think the thing you mostly would want to be worried about is that you're not stretching or straining any muscles or any other tissue in the process of attempting the crack. Whether there are any long-term implications has yet to be seen, and I don't think dislocation is even in the realm of possibility of what could happen as a consequence.

I must not be visualizing this correctly – how does the placement of the left foot affect the process? When I put it behind my right knee and bend forward ... I'm just bending forward. There's no strain on any joint. There's also very little leverage to put any pressure on any joint, really. Maybe this indeed doesn't work for guys? :?

First: What an incredible website!

Every day I tend to crack the following things (probably a dozen times throughout the day… it's hard to move without something being ready to crack!) and am looking for more to add to my list:

Back/spine - upper, middle, lower. There's one all the way at the top, seemingly right where my back meets my neck, that I have to do while on the floor, and is the only one that just seems totally unsafe

Neck
Jaw/ear (both sides, two distinct cracks possible)
Elbows (real cracks, not just the sort of clicking noise that you can sometimes repeatedly make with joints)
Wrists
Fingers/knuckles (3 each, I would assume). I tend to crack my fingers in one motion that does 2/3 joints on 4 fingers all at once. It's pretty glorious.
Knees
Toes (1-2 joints each?)
Foot (have no clue what I'm cracking, feels like the base of the big toe probably, but I feel it way below the actual toe)
Ankles

I don't think I've managed to crack my hip yet, but am intrigued. Shoulders seem like an obvious area for expansion too...

And again, I do a lot of these probably 5-6 times each day. We'll find out if the whole arthritis thing is a myth or not in 30-40 years