I think the worst experience I've had on MFC was with a model that encouraged members to troll each other.
A few months after she'd started, she'd picked up an assortment of regulars and one big tipper that liked messing with other members. At one point, the big tipper convinced her that it would be fun if members could tip against each other's tip requests. His first few attempts were playful, cancelling others' song requests and joking about their taste, but he was establishing a precedent...
One night when she'd set a countdown of 2000 tokens, the big tipper wasn't around, but the regulars came together and brought it down to 500 in the first half hour. At that rate, we'd have been done in a matter of minutes, but the big tipper wandered in and tipped 1000 tokens against the countdown. Seeing as we'd just lost two thirds of the progress we'd made and had no realistic prospect of finishing while he was there, the rest of us gave up - she went another half hour without a single tip. Then, despite the fact that we'd tipped 1500 to the big tipper's 1000, he convinced her that the "deadbeats" weren't going to finish her countdown, so she should skip it and go private with him instead, effectively cancelling all of our tips for the night.