A lot of them are from 3rd world countries from what I've heard (not the countries they are claiming though). They just put people on computers and make them look up email addresses to try and find a sucker. My grandma would probably fall for this stuff. Me though, I just mess with them and act like they've got me.
On a side note, I've seen some big truck pass my house about 5 times now... My dogs keep barking and it's a huge truck. We park our cars in the garage now so maybe they think nobody is home. If they pass again I'm pulling out weapons....