I had my gallbladder out when I was 21 (I am now 40) and I am still experiencing rapid dumping, painful diarrhea and going to the doctors to figure this out. I can't believe that this is all from having my gallbladder out. Every time I eat anything, no matter how small, I end up in the bathroom in alot of pain. For a while I was on Colestid and that helped alot, you may want to try that if you dont mind taking a very large pill every day. It does help because it binds with the bile in your stomach or so I'm told.
They say that Diarrhea is only present in 10% of patients post gallbladder removal but the majority of people I have talk to have had diarrhea from day one post op and still have diarrhea 2 to 3years later post op. The best thing to do to prevent it is to eat small meals and to eat a low fat diet.