But it is significant that the release of DRM free music did not increase those files prescence on P2P:

"As for the effect of DRM-free on content misuse: the online media measurement firm BigChampagne has been keeping a close eye on EMI-owned content since the DRM-free launch, and its CEO Eric Garland says that the effect on P2P traffic has been statistically insignificant. He adds that there is little overlap between people who purchase content on iTunes and people who upload files to P2P networks like LimeWire, so therefore P2P piracy is not likely to be affected one way or another by content protection methods used in the iTunes/iPod universe."

DRM costs some money to implement, so if it doesn't do anything for a business, they will just ditch it.

Also, as the public gets used to DRM-free music it will become harder and harder to but the genie back in the bottle, and their acceptance of DRM'd music will become much less, I suspect.