It depends on what the person did. For example, if one was using a gaia gold cheat, they have a chance of being blocked from gaiaonline permanently.
utube
Well they don't tell you if they blocked you obviously, because it's a concern of privacy, but you would know if they blocked you if you sent a message or something like that and then if there's no response after a long time, then you know that they blocked you. :P
yes
Tektek.org
It gets blocked.
Chaos-programming is a good proxy
If you have blocked them, then you can't see them and they can't see you.
Usually it's the account, not the computer.
nope
no they can not(:
You can ask them.
You sure can, then if, in the future they unblock you, you'll still have them blocked.