What happens when you block somebody on Facebook or Twitter?

[Victoria]

I used to talk to this guy who I met on a dating site for about a month or so but I started noticing little things about him that I didn't like so I so I blocked his number out my phone. Come to find out months later he has still been looking on my pages frequently which I NEVER gave him. So I blocked him on my Faacebook along with the site we met on Tag. Well I guess he found me on Twitter. So I blocked him on that too.

Now i'm curious,
what happens when you block somebody on Twitter along with Facebook?

[george]

When you block someone, they can't see anything you post. They also can't find your name and profile in a search.

[Havoc]

Blocking someone makes it look like you don't exist to them from whatever website. They can however, make another account and view you. So set whatever privacy settings accordingly.

[Ashleigh]

if you block someone on twitter they can still see your tweets if they type your username in the search part of it. but on facebook they can't contact you in anyway and cant see your statuses or anything like that.