Radiohead did it with In Rainbows, some rapper (who was working with Trent Reznor) did it and now NIN has released Ghosts I-V as a digital download.
In Rainbows was a massive success with many fans opting to pay for the album, NiggyTardust not so much (only 1 in 5 people paid for the album) and it is yet to be seen if Ghosts is sucessful.
Can you see this being the way of the future with album releases? I can definitley see this catching on, maybe it's a better path for already established bands to take rather than somebody releasing a debut album.