The first time I ever heard of one of these I was in Laughlin, NV at the Flamingo Hilton. There were only 2 NBA games left and it was when Jordan was with the Bulls. I wanted to take the Bulls in the first half, and the game, combined with the Lakers and over. When I tried to put it in, they said it was a "correlated parlay", I said "God Bless You" and give me my bet! They said they couldn't! I talked to the sports book manager and asked them why I couldn't put it in. He said "blah, blah blah" and I couldn't do it! I said if the Bulls don't cover the first half, I would lose as it would take out the whole four teamer! The result was, I took the Bulls and the Over, and the Lakers and the Over, and wound up winning anyway!
For some reason, a book that a lot of you bitch about, Bodog, takes these all the time. I think that Sportsbook.com takes them also! I've never really understood the fact that books won't take them, other than the hedging possibilities. But if you knock out the first half with a loss, it takes apart the whole parlay! Go figure!