If you're a musician, what is the number one, most important thing you will do for your music career today? No, not tweet or Facebook or blog or engage in a debate whether the internet is good or bad or contact the press - it is working on your music.
Wait..what...huh? But what about your digital marketing strategy and building your fanbase and designing your merch and all those other things on your to-do list? They matter, absolutely. But remember WHY you're doing them - you're doing them because of your music, and if you don't have the music, then you can social network your little heart out, and you'll just have lots of online friends - which is not the same thing as having a music career.