Yep....happened last fall around the start of the NFL season. He took their sports FP but they offered a casino FP as well. I don't remember specific amounts, but the gist of it was he rolled the casino FP and ended up with a profit. That converted to cash and they forced another 30x roll on the cash, which ended up being a loser and dipped into his overall cash balance. I had never heard of this before but I just looked at their website and see mention of double roll. Basically they are getting players to risk their general (sports) balance if they make anything on the casino side.
Again, people have to read the rules but this seems fairly predatory and should be spelled out at the time of the bonus IMO.