With a brand like Lil Wayne, you don't need to spend money on advertising to gain FB users.

You're severely underestimating how popular these people are. Plus given their target markets ARE the social networking generation, getting them to "like" your pages is even easier.

It would be a waste of money to spend anything on trying to get FB fans when you can do it for free.

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Its all about finding all possible ways to distribute their content + maximizing the interactions with the content once you send the traffic (optimizing it to be viral, social, and a great experience where both the fan and artist are happy).

Well, I assume Lil' Wayne's advertising budget went to these guys, but then these guys didn't spend any of it on the promotions they did (it just paid for their time / expertise).