That's what's "in it" for them.
That...and miles of dick.

Why do only the reviewers benefit from the 750,000th review? Without the ladies we would have nobody to review. Anyone else feel this is unfair? Whats in it for the ladies?

Perhaps if the 750,000th reviewed lady got something too?

It seems that you advertise on enough TER boards that you apparently feel that you get something out of the deal.

Think they're 'in it' to spread love and joy?

Some, maybe. But that's not all they're spreading, and all of them definitely not without $$$$ behind it ...