They aren't totally legal, but a lot of them are actually encouraged by the labels. They seem them as a free way of getting singles by new bands out to a huge audience, and in return for that, they mostly look the other way when the blogs distribute works by bigger artists.
It's a gray area, but one that's been a very good marketing solution for labels -- especially smaller labels.
iTunes Top Downloads -- November 16, 2008 This is a moment in time snapshot of the current top downloads from iTunes. We take a snapshot each week at the same time and post it here. To preview the songs, click on a link.