PR is right on this one. i remember a study in the nfl a few years ago where they broke down fumbles and their conclusion seems to be in line with player's. although i think they combined rushing and receiving fumbles and compared them to punt and kick return fumbles. but the percentages weren't real close. something like 1% of all touches running and receiving were fumbled and it was as high as 6 or 7% on all touches kick and punt returning were fumbled.
makes sense when you think about it. basically you got 11 guys trying to kill you every time you return a punt or kick. well...10 and a half considering the kicker. there would be a lot more fumbles if every running back faced 11 man fronts.