Someone on Facebook who consistently has a profile photo of anything but themselves - e.g., almost invariably a toddler, but a vague group photo, a photo of a cartoon, landscape, a flower, their feet, generic artwork, animals, etc., are also par for the course. Very often these individuals don't ever make a peep to you directly after they're let in, and instead enjoy quietly watching what the people on their own friends list do instead. Blowing the image they'd like to project of being "too busy for Facebook," they somehow notice within hours or even minutes after they've been deleted.
Michelle: "Janice is such a Facebook hider. Did it ever occur to her to use a photo of herself WITH her kid as her profile pic?"
Miranda: "Nobody does that! You're crazy."