No, they don't take just fake likes. I am more then sure about this.
Recently I started a new Facebook Fan page, with zero likes.
And I started to promote this page only with Facebook Advertising Platform.
I never bought likes for this page or anything like this, the only thing that I did was to Invite my Facebook friends and thats it.
It is been 2 days that Facebook is removing likes from my page, smth around 100-200 likes.
Now I am pretty sure that I don't have fake likes, because they are all likes that came through facebook ads, real people that saw the ad and likes the page...
Facebook removes even real likes time to time, don't know why but they remove them.
I don't think that for 2 days, 100-200 people deactivated their accounts, so this is not an option
Don't think that 100-200 people unliked my page too, because I wasn't posting too much either.
Anyway, what is mos important, Keep it going, if the likes rate is bigger then the unlike rate, you are in a good position...