I guess lots of bands do this sort of thing, but it’s the first I’d heard of it. The Barenaked Ladies are launching a cruise in January, 2007. It’s called Ships and Dip:
The band will perform multiple concerts and multiple trips to the buffet, and, in between, you will be treated to a truly Barenaked experience. From intimate solo shows to jam sessions to a rollicking karaoke party with BNL, Ships and Dip is a must for the true Barenaked Ladies aficionado. Friends of ours from the worlds of music and comedy will be announced shortly. And don’t forget, everyone has to have a passport!
Why would they do this? For the money, presumably. Could the money be that good? It’s US $1500 per cabin (assuming two people per cabin) for a four night cruise. The ship has about a thousand state rooms, and apparently the cruise is rapidly selling out. That’s $1.5 million gross revenue, but who knows how much it costs to rent a cruise ship for five days?
Is there any band I would suffer a five day cruise for? Probably not. I don’t think I’d want to see even my favourite bands more than once in a week. I’d rather pay $1500 to, say, have dinner with a couple of my favourite musicians.
DarrenBarefoot.com 
The cruise is only 4 days long. I’m paying a lot less than that to go on an eight day cruise. (It’s funny how you’re willing to do things you swore you’d never do once you have a kid and off-the-beaten path travel becomes challenging.)
The sponsors probably approached the cruise ship via a “convention/conference at sea” program. When I had a 9-to-5 desk job, I used to get lots of invitation to software conferences on cruise ships. Ah, for the days of the tech boom!
‘suffer a five day cruise’
Tell us more – I’ve always been under the impression that a cruise would be rather enjoyable, but there seems to be a large number of people who really disagree.
Jeff: Coincidentally, I answered that very question in a comment a couple of weeks back.