I don't think fat causes gallstones, but increased fat in your diet may call for greater amounts of bile to be squeezed out of the gallbladder. This may make any stones you may have more obvious.
I had gallstones and a gall bladder removal after about 13 or so years of eating very low fat. Fat definitely did not cause my problem. I also had several acute pancreatitis attacks during those years. A medical doc I just spoke to the other day told me that we now know pancreatitis is tied to gluten in the diet.
Robb Wolf keeps bringing up that gallstones are very closely liked to gluten intolerance... just saying.
I never had problems with my gallbladder until I was eating a very lowfat diet of unlimited fruits and veggies for a prolonged period of time. Needless to say, the doctor yanked it out before I knew enough to protest and insist on removal being a last ditch effort, if an option at all.
If it did then I'd surely be affected by now.