I have a few people I message regularly, or close, we are friends. Others are questions from my reviews, my students and ideas I might have for others to answer. I do send random cute pics to people.
I was messaging ridiculously to stainedclear, so much that we finally decided to exchange phone numbers I get messages often enough. I keep in contact with my students and I like to talk private about somethings, but I comment more on walls.
I message a lot but also comment on walls and post on the forums. Like beck said, we used to message back and forth so much that we finally just exchanged numbers. LOL Sometimes it's easier to message than post on a wall, especially if it's a private conversation.