Understanding the difference between publicity and advertising can save you thousands of dollars in music promotion. I had a client that wanted to promote a mixtape and he wanted me to give him tips on facebook ads. He gave me his budget which was $1,500. With $1,500 on average you probably would get around 7,000-8,000 likes on facebook. I said why don't you try hiring a publicist for $1,500 for a month or so you could probably get about 1 million impressions or more. So he ended up doing publicity and he got placed on some of the top blogs. So for $1,500 he reached around 500,000 people. Big difference from 8,000 using facebook ads.
So I'm not saying ads are bad, just saying know the difference because if your building your facebook likes thats one thing but if your promoting a particular project a publicist might be better for that.