Abnormally rapid increase in FB likes.

Hi,

I've been adding FB likes to my pages for a while using Like4Like and AddMeFast, and generally I can get quite a few likes in a day from it.
But I've just seen one page (which I'm not managing) go from 3 likes to 2500 in a matter of an hour. How is this even possible? Are there other ways of increasing the page followers rather than using these sites such as L4L and AMF?

Thanks a lot.