Check out this page that describes many of the "more than one" pedal vehicles that now exist, and here's a place in Austin that rents Conference Bikes. Even the beer bike is there. (And I'm sure they've ironed out those sticky legal issues by now.) Can't you see that pre-touring the mardi-gras parade route this spring? Or how about a fleet of Conference Bikes, or 4 person surreys to rent for our own Mardi Gras, Cyclovia season?
In the long term, though, bikes that are tricycle tandem or surrey models might be just the thing to give seniors, families, and more safety conscious types the confidence to pedal.
Cities have been known to buy experimental vehicles like these and rent them out or use them for special occasions, a bit like Shreveport did with the downtown trolleys. A bunch of partying friends likely wouldn't be able to rent the trolleys out though.
I'm gonna be on Sanibel Island in Florida soon, where I hope to rent a 4 person surrey for my family. I expect it to be fun, social, relaxing, good exercise, a bit slower than regular biking, but still a lot faster than walking. I'll post on what it was like.