Does anyone know a few things about twitter?

[TMI]

When you tweet who sees it? I tweeted before anyone was "following" me. Who saw it? How did people see it to follow me?
How many times does it keep coming up? I will get a notice of "20" new tweets by someone I'm following, but they are all old. Yesterday's same news actually. I have the same question about facebook. For both, how many times does your message repeat?
THANKS! AC Milan 91! On facebook, do you know if you remove all messages from someone, can they tell you removed their messages? I don't want to offend anyone.

[AC Milan 91]

Tweet example: 'Yahoo answers is cool'

As no one was following you when you tweeted, it won't appear on their homepage when they start following you.
The tweet will remain on your profile(unless you remove) and they will be able to see it if they go to your profile.

Also, if people search for 'yahoo' or '#yahoo' on the search box, your tweet will appear in that list regardless if they follow you or not. (These are hashtags in case you didn't know)

You can make your tweets private to the people that follow you only, so they can only see your tweets after they follow you.

Messages will never repeat on twitter. Unless no one has tweeted in that time, the message will remain in that spot, giving an illusion that it is repeated maybe. Or someone may have Retweeted the tweet, so it goes back up.

In Facebook, messages may appear on Most recent AND Top news if it has quite a few comments or likes.