Was it Flea from Chili Peppers who released 6 in a year??
John Frusciante. I haven't heard any of them, but I heard they weren't bad.
I've listened to a couple of them. It's kind've iffy stuff. A lot of it either sounds incomplete or will completly depend on your mood. He also aimed for 6 in 6 months but I believe the actual releases spread out into 7 or 8 in the end.
I'ld have to say Madonna has a pretty big profile. As do The Who and Queen.
The reason I think that artists don't release albums as much now is because their's quite a lot of attention put on tours now. It's also pretty much how bands get their income these days because of how easy it is to steal music these days thanks to the internetz. Back in the 60s it was mainly a "produce a few singles, then filler songs, quick tour for screaming girlies, rinse and repeat" circle from what I've picked up. But what do I know eh? I wasn't exactly alive back then.