There are many Cousin Bait success stories out on the internet. There are also several definitions.
My genimate from Texas, Amy Coffin, says that with Cousin Bait “you’re fishing for cousins so you can compare information for your respective family trees.”
In her post here she describes how she Reeled in a Big One.
1 March 2016 Update: Thanks to Geneadictionary supporter, Tony Proctor who has found that the term “Cousin Bait” was first used by Greta Koehl on Greta’s Genealogy Bog (that’s not a typo) on 19 March 2010. (http://gretabog.blogspot.ie/2010/03/family-and-friends-newsletter-friday-19.html)