As of sometime in 2010, there are 200 million Twitter users. Sorry I couldn't find a more recent figure (it would have gone up a lot since).
A lot of people have a Twitter. Four out seven people in the world have a Twitter.
To message people on Twitter, you must have an account.
It's impossible to know exactly how many fans she has but she has 3,876,728 fans following her just on Twitter.
Manny who? Maybe Manny loves wearing sunglasses. Seriously, a lot of people wear sunglasses for different reasons.
I have been stalked on twitter but most people aren't.
Yes, you can actually know if someone retweet or mention you in twitter. It is a default feature in twitter and every tweeple (twitter people) can know who followed and mentioned them.
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Manny there a lot of people but manny is Michaels BFFL
Yes, the site Twitter is a social network
No he did not, "his" Twitter was created by his PR people.