Susan Boyle has released an album. It has broken the world record for most Amazon pr-orders. That is a pretty phenomenal feat. I checked out the track listing and got very annoyed, because it's just full of covers! It really makes me angry when musicians just take someone else's creation, re-record it, and sell it.
If they change it significantly (a great example is Ryan Adams' version of Wonderwall) then I don't mind - that shows creativity and talent. Just singing it again really doesn't, and that's what Susan Boyle has done. It's also what Leona Lewis did with Snow Patrol's 'Run', and her version is far inferior to the original.
It takes far more talent and work to create something new, and I am in awe of people who can do it. It takes very little talent and work to just play something someone else has written. To be brutally honest, I could do it, with a bit of time. People shouldn't make money from covers. End of.