I found a site with a number of joint cracker testimonials.
The following quote from Matt Furey is very interesting and needs to be followed up:
When I'm in China and go for my daily massage, the lady always cracks the knuckles on my hands and feet. In fact, she snaps them and pops them in a way that would make ole Sister Synesia (and yes, that was her name) cringe.
And do you know - in China - cracking of the joints is NOT considered bad manners or form. It is a health practice.
Cracking your knuckles opens up the meridians of the body so the chi can flow the way it is supposed to.
So I recommend you do it daily.
A teacher at my old high school was a licensed chiropractor and he always told us that cracking your knuckles wouldn't cause arthritis, no matter how much you cracked them. So the Chinese are right once again.