Uh...the people who didn't download it for free, which was a LOT of people, probably believed they were going to get the entire album? Some people even paid around the cost of the CD.
I know, I struggle with the fact that people payed for the low quality downloads too.
These people are known as 'fans'. Fans pay to support their favourite artist. Then, they had to pay a second time, the full retail price, as the mp3s they had payed for were finally revealed to not only be rather terrible quality, but missing part of the album.
"Bonus Tracks" was a nice way of saying "The version you payed for first isn't the full album, but if we say it like that, there will be a riot."
People seem to forgot about that Saul Williams album, that was also free, but offered the entire album at 192kbps, 320 kbps or FLAC lossless. I think that was taken down after 100,000 downloads, but I still believe that this was far more noble than what Radiohead did.