They've been known to go as far as buying domains for the restaurants and hosting the menus on them, basically inserting themselves as a middleman, then threate

They've been known to go as far as buying domains for the restaurants and hosting the menus on them, basically inserting themselves as a middleman, then threatening the restaurant with consequences if they don't pay up for the favour. This might be accompanied by the service taking their cut out of every meal ordered through the site, forcing the restaurant to lose money on the orders. That's not just listing, it's a racket. GrubHub was caught doing this, I believe.