I bought some likes for a couple Fan pages a while back and the funny thing is you can actually market to them. But one of man fan pages had over 2600 likes and now it has alot less and this REALLY messes with the PR.
I would highly recommend getting natural likes to your fan pages. Facebook doesn't like when you buy likes lol. In the long run it's worth waiting for real people interested is the niche or content on your page!