I once spotted a very foxy young lady on OKcupid who was supposedly into "casual sex". Way out of my league, I don't know why I even bothered to message her, but I couldn't resist. She didn't reply, and her profile vanished, she had blacklisted me (that's what blacklisting does on OKcupid).
About 9 months later, I saw a familiar face on AW. I booked her, and got to shag her after all! But I kept quiet about spotting her on OKcupid. I must admit that I got a secret thrill out of giving one to a girl who had blacklisted me, I'm pretty sure she didn't recognise me from my old profile pic. Sadly she disappeared from AW not long after.