Quick: if I asked you “Do you use an Internet service or site to share updates about yourself?”, how would you answer? “Yes: Facebook,” “Yes: my blog,” “Yes: Twitter,” (yes, all of the above)? Okay, let’s say I took all of those yeses, no matter which site/service you use, and declared them all to be Tweets.

Face it: someone with that little regard for the differences between the above types of sites probably shouldn’t consider himself/herself to be an Internet researcher.

19% of Internet users answered yes to the question “Do you use Twitter or another service to update your status about yourself, or to see others’ statuses?” in a Pew Internet & American Life study, up from 11% in April and last December. Naturally, Pew concludes that all 19% of them use Twitter. Brilliant. In fact, they’re so confused, I’m having a hard time figuring out these stats. They’ve mixed up the data so well that I can’t tell whether they mean “update their status” or “actually use Twitter” whenever they talk about Twitter use.

While we all like our sites to have visitors, a loyal visitor—one who returns for later visits—is especially valuable. And while search engines do send a lot of visitors, a study issued by Chitika earlier this month shows that the most loyal site visitors come from social sites, as eMarketer reports today.

Studying 33 million uniques across its publisher network last month, Chitika used the criterion of four or more visits over the course of a week to indicate a loyal visitor. They found that Facebook and Digg had the best loyalty rates:

Facebook showed 20.69% of its referrals became loyal visitors. Digg had slightly over 16% of its referrals visit four or more times that week.

Interestingly, Yahoo had a slightly better loyalty rate than Google.: