I'm torn on coleslaw on BBQ. If I'm making the sandwich, there's not much chance I'd put coleslaw on it. But if I'm in Memphis, I'm not going to order without the coleslaw, mainly because I figure they've constructed the flavor of the sandwich to include the coleslaw.
I've only been burnt on this theory once, at a place on Beale St. It was kind of a gimmick restaurant and I guess they thought the 'dry rub' thing meant to put it on EVERYTHING. I mean they actually shook dry rub, uncooked, all over the sandwich and on top of the coleslaw as well. It was horrifying. So it really wasn't the coleslaw at fault, it was some moron owner thinking they knew what BBQ tastes like. It looks like they are still in business and I can only attribute that to the captive tourist trade on Beale.