We're very preoccupied with maintaining the privacy of our users, so we do not track who comes and downloads; it is anonymous. We get occasional feedback on the site that says, “I'm interested in this data set. Can I have it?” We have their e-mail addresses for the purpose of responding to such e-mail, but in general, we do not track who is accessing what data. It's anonymous.
We suspect it's a lot of academics and students and non-profits and so forth.