I had a girlfriend years ago that was an extreme optimist. She was a very intelligent person, very outgoing and very successful. She believed everyone was good, and no one ever did anything bad. We got into an argument once over this exact same thing - she thought she'd won a new laptop from some sort of popup ad; all she had to do was fill out some sort of form with a bunch of private info. I told her it was an obvious scam, and she got really defensive, telling me that I'm always so cynical and if I expect the worst from people, that's all I'm gonna get. I talked her out of submitting the private info to the form, but yeah, I can totally understand how reasonably intelligent people would fall victim to something like that. There's different motivations, but for my ex-girlfriend, it was her refusal to accept that people can be bad (take advantage of others).