This article is a guide to how DRM controls the market place.  The article shows how music services that consumers pay for give their customers less than they promise because of copy protection and the DMCA.  The guide explains the restrictions of various music services and how the services cover these up through marketing.  The first service is iTunes.  Even though you purchase the music through Apple, iTunes can change the DRM whenever they want, thus they can change and limit what you can do with music that you own.  Apple also limits first sale, backing up, remixing, player compatibility and format conversion.  Even though you own the song, the DMCA allows Apple to control the music that you purchase and restrict your uses of it.  
Microsoft’s “Play for Sure” claims that Windows Media Player’s DRM allows you to choose your music and devices.  However, there are still severe restrictions because of DRM.  There are very few players that are compatible to play with the WMA DRM format.  If you want to use a player that does not support WMA content, you have to repurchase your library of music.  Even though Microsoft markets their DRM as user friendly and non-restrictive, it is more to make DRM a norm than the truth of the matter.
RealNetworks markets their services as compatible with any MP3 playing device.  This in fact is not true, because music purchased through RealNetworks only plays on devices that support their DRM or the WMA format, thus limiting the players that the songs can be played on and restricting use of their music. RealNetworks, like iTunes, limits the number of times you can burn a song as well as the number of backup copies that can be made.  They reserve the right to modify their DRM and what it controls.  RealNetworks also does not allow reselling or remixing songs purchased through them.
Napster 2.0 advertises itself as a service that allows you to have all the music you want in anyway that you want it.  It offers three services and all charge more for uses that were once free.  Napster Unlimited allows you access to all the music you want until you stop paying the monthly fee.  You also have to pay if you want to put it on a device, which can only be one that supports WMA.  It also costs money to burn it.  The DRM restrictions can change, you can only backup a limited amount of times and burning is restricted.
    I will use this article as an example of how companies use DRM to exploit the music market place.  Each service limits the music they sell so that it can only be used with products that they license.  They also limit what a person can do with the music, even things that are traditionally acceptable under copyright law such as making back up copies and the first sale doctrine.  This article shows how the DMCA changes traditional copyright laws and allows companies to exploit their customers.