Have you ever wondered why people follow you on Twitter?
How do they find you?
There must be people out there who are constantly searching the Tweet Waves for particular keywords because:
a) They are interested in the subject.
b) They are trying to sell you something, and therefore want to find you to sell said something to you.
The first reason is quite obvious. I like superheroes and I'm interested in the ebook world, so I'll often search for "superhero", "Kindle", "Kobo", "ebook" etc.