From the article:

At Second Source, the best customers were the most desperate. Often they were immigrants with poor English. Brokers bragged about their biggest rip-offs. For motivation, Hurwitz would tape $100 bills to the wall. Salesmen who weren’t cutting it would have their chairs taken away. “Why are you sitting on my chair,” Hurwitz would yell, “if you’re not making me any money?”

I'm sure those businesses were not physically forced to sign but I'd wager those phone calls were not entirely forthcoming on details as well.