I've noticed that they tend to have something in common with the person that you've just messaged. Location, height, body type, age... any one of those things will have the profile showing up in that section.
Or (horrifyingly) is it to stop idiots from obsessing (and sending hate mail if they don't get a response within 5 min) about the person they just message'd by distracting them with someone else?
Didn't you get the memo? You're suppose to follow up every five minutes until you get a response... 