(2007.04.02) Apple unveils DRM-free music on the iTunes Store from EMI
(2007.08.13) Google, Universal Music Partner to sell DRM-free music
(2007.09.25) Amazon announces DRM-free music from Warner Music
(2008.01.04) Sony BMG confirms DRM-free nusic downloads…
But will force customers to visit a offline store to buy it
(2008.01.10) Napster to Sell DRM-free music
Additionally there are signs that the rest of the industry will soon follow.
Now how does or did this affect the sales?
Example: Sales of Pink Floyd’s Dark Side of the Moon were up 350% after its iTunes re-release without DRM! The consumers seem to favor the DRM-free variety of digital music, and have proven willing to pay for it…just as they did with CDs (which are, by nature, DRM-free).
(DRM Source) wikipedia