You will get very weird results from that depending on your song library. If you have every song from a prolific artist, and one to two songl you like from a few other artists, you'll get a nice random distribution among artists, but not among your library. For very lopsided libraries, such as people that just started a service and maybe have added one or two full artist catalogues and a smattering of other songs they like that they thought of (which I imagine isn't all that uncommon, it's the state I commonly find myself in on a new service), it will result in a lot of repeats and ignoring a bunch of your library.