The Pros and Cons I could think of are:
1- If you give something to everyone, the reward is spread tooo thin to be attractive. 2- But if you're giving something to everyone who signs up and performs an action, people may think of it as sure fire money for which they dont have to wait for a contest, etc.
Can you guys share your opinion on it as well? It'd be great if you already have some experience running this sort of campaign.