I have, first just out of curiosity and once to show a friend of mine an image of her.
Occasionally now I do when I want to see her face. Like the other person in this thread, I do it when I need a pick me up, literally just a friendly face to remind me of good fuzzy feelings.
She has a Facebook but her online profile is very guarded. I see that she has lots of friends, that's about it. I wouldn't want to intrude beyond that.