A popular MMORPG went through a period of not enforcing rampant botting, gold farming, and similar activities which provided a substantial boost to their user numbers. A short time after the acquisition, they announced major initiatives to combat botting, bringing the user count back down.

IANAL, but couldn't this be fraud?

It would depend on how they presented user numbers in the merger discussions I think basically. If they promised anything about how organic the users were or suggested they were well paying for revenue projection purposes?