I put MP3Dollars on my one page mainstream site that I pretty much ignore so I don't really have any useful info to give you on that other to say it looks like it is a good program and something different so why not give it a try.
I was reading on CNN the other day that 90% of the world's population has never been on the internet yet. Wow that sure speaks well for future growth!
On the subject of iTunes it is legal because Apple has reached agreements with the musicians in order to sell their music. This is also what is keeping them from going worldwide with the service since they have to negotiate country by country for each band that they are able to sell, but they are expected to go worldwide sometime next year.