Lets see: One of my friends is extremely good with a computers. He's writing a book about how to program and use a certain device that I'm not going to name so you don't figure out who he is. Another one of my friends knows enough about computers to not get viruses (although he does use a Mac), another one knows his way around computers very well (he's much more knowledgeable on networking, I think) too, and wouldn't download a virus. Then there's one friend who got a virus on his laptop (lol). My dad knows computers well enough not to download viruses, I think, and my mom hardly downloads things except like PDFs or some kind of documents, and she uses a Mac as well.
Yeah, I know Macs aren't impervious to viruses, but there are noticeably fewer Mac viruses than Windows viruses.
And I'll admit, I've gotten a few browser hijackers before I knew to uncheck or bipass certain installations.