okay, let me clear a few things up. Note: before reading this post, please note that this is as far as I know.
After I created an account on there out of curiosity, I did a little exploring. There are 4 main pages after you have logged in: home, education, tech, and the last one I can't recall. So, taking my curiosity further, I went into the education section, and found 4 pages, one of which I explored. There's a units page, a books page, and the other 2 I can't recall. I went into the books section and discovered you could upload a book in 1 of 5 formats. That's all I have done in exploring of the sight as of right now. As to the worry of you getting a virus, or perhaps getting spam e-mails, I have received none of these so far. I have not received any calls from unknown numbers. I hope this will take away some of the worry in this topic.