Like I said, the greatest proof that restaurants don't want their patrons paying for reservations is that they don't do it. They already have what they need: a way of recording reservations and a maitre d' with knowledge of their business and a triple-digit IQ. They know there's demand: many people already try to get a table on a busy night by slipping the maitre d' some cash. If they wanted in on it, they'd already be in on it, and you'd be stuck trying to convince a restaurant to hand over control of a simple, vital, near-zero-cost part of their business to a third party for no gain. I maintain that you could only survive as a parasite by avoiding notice and/or paying off the right people.

Restaurants are in the business of filling their tables by making customers happy -- those customers will return, tell their friends, and the tables stay full. By filling up available spaces (thus resulting in customers being told that a very long wait is to be expected) and providing a paid line-cut (who enjoys being cut in front of while waiting 60 minutes?), you're going to make a lot of the restaurant customers unhappy, both directly and indirectly.

If this was an ethical business, they would have told the restaurant what they were doing and received approval before they decided to lie to the restaurant to achieve their aims.