Yes, be careful. Though I want to point out WHY these scams are so successful:

Don't let greed blind you. Let's be realistic, for those of us who have been scammed, its not like we didn't see any red flags. But we got greedy, we imagined the money we might make and rationalized away our uneasiness.

Pigs get fat, hogs get slaughtered as the saying goes. Stay safe, and use your head.