I remember 15 years ago on the Internet it seemed like every mailing list or discussion group I was on there would be the people trying to work into the conversation that they were in Mensa. Of course for everyone else this was like having a flashing sign on your head which said "wanker".
I used to be in MENSA in my early teens. All I got for my 25 pounds a year was a magazine every three months. I decided after a couple of years it just wasn't worth it.