So I have to admit that I'm a big teknophile and big advocate of online music downloads.  I think that many music lovers will agree that the advent of online downloads is such a great concept.  You have the ability to preview and purchase songs from the convenience of your living room.

However this emerging industry has some big hurdles to overcome.  The biggest complaint I have is the lack of intercompatible  DRM format.  DRM is basically a security mechanism that let's the content publishers (the online stores in this case) to control what kind of rights you have to your songs that you purchase (burning to cd, transferring to portable devices, how long you can have the song).   Almost all legit online music stores use DRM.

Now the problem is that there isn't one DRM format for all the online stores.  For the mostpart, you have two major formats for DRM.  Microsoft DRM and Apple DRM.   Most of the online music stores such as music.msn.com, napster, musicmach.com use windows DRM.  Most of the media devices you find on the market support this format (often referred to as protected WMA format). 

Apple on the other hand uses their own DRM format (protected AAC).  Apple does not let any other software application, online music store, or portable device maker to use this format.  Only Apple iTunes is allowed to sell songs in this format and only Apple iPods are able to play this format. In addition, the iPod will not play any other DRM format (especially WMA from Microsoft)

So why has Apple been so successful?  My opinion is great marketting and a great product dispite the limitations of compatablity.  From everyone I've talked to, the iPod is the one of the best portable players on the market and the ease of use when combined with iTunes music downloads.   So with their success, it's not suprising that they don't need to open up their iPod to competition from competing online stores.  However, in the long run, I think it would promote the sale of their ipods for those of us who won't buy one because of the lack of online stores it supports.  Hopefully music stores and media device makers can come to a common ground and adopt a universal DRM format that anyone could use.  

More Info on DRM issues:

International Digital Media Project (DMP)
Mission: To promote continuing successful development, deployment and use of Digital Media that respect the rights of creators and rights holders to exploit their works, the wish of end users to fully enjoy the benefits of Digital Media and the interests of various value-chain players to provide products and services.

DigitalConsumer.org
Mission: To restore the balance between citizens and copyright holders by employing a Consumer Technology Bill of Rights.

Electronic Frontier Foundation (EFF)
Mission: Working to protect our fundamental rights regardless of technology; to educate the press, policymakers and the general public about civil liberties issues related to technology; and to act as a defender of those liberties