how to connect two people in your website

Question

There is a game called Verbosity (it's a Game With A Purpose) and it's on this link
www.gwap.com

in the game they connect two players randomly to play with each other, the game is that player1 should describe a word to his partner(player2) and player2 should gues the word.
I'm trying to build a website that do something like that, but I wonder
1- how I can connect two players randomly to let them play together although they are not registered users ( they are just guests to the website )?
2- how to make them playing in private game, i mean each two players are playing their own game?
3- What would I need to use? Is it enough to use ASP.Net? Do I need silverlight?
Thanks