Mar 10 (2013) it looks like 1500 fake fans were purchased taking likes from about 300 to 1800. Then on Mar 24, 400 fans disappeared at once. Did Facebook possibly identify a ton of paid likers and remove their likes from pages?
The red unlike graph indicates a dip, but it's only 38 unlikes, not 400. Another dip 5 days later with 88 unlikes.
Then around Apr 20, there's a temporary increase of 200 likes which are removed two days later.