I just read on a blog that Facebook advertising revenue is quickly surpassing Myspace's. It is no surprise since Facebook seems to be more widely accepted than Myspace. http://www.clickz.com/3635971?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+clickz+%28ClickZ+News%29&utm_content=Google+Reader
I personally would advise clients to advertise on Facebook for most tactics unless the business wants to target musicians or teeny boppers. What do you think?