What I've found is that there are a lot of business/specialty type Twitter users who follow gobs of people, and if they don't get a follow back in a few days, they unfollow you.  There are definitely some people who are in it for the numbers, and do away with you if you don't follow back.

The same exact thing happens to me.  If I sign in to Who.Unfollowed.Me, I'll always see like 10-15 people who unfollowed me, who I wasn't following, and they are all businessy types.

Exactly what Liz said..  It's definitely a roller coaster with the follows and unfollows.

I went out of town for a few days and  didn't have access to a computer,  but when I returned I noticed I had lost at least 20 followers.  I'm assuming it was because I had been "quiet."

Find a group to tweet with regularly; join a few twitter parties & you'll get a group of followers & it won't matter what the numbers are.

If you wanna find me, I'm @mycrazybusylife

I've noticed the same thing, so I don't pay much attention to the numbers on Twitter! I do pay attention to who I follow back, though, and if they seem too businessy, I don't follow them. I'm still trying to figure out how to use Twitter effectively!

Ditto what everyone else said!  I try not to check my Twitter stats since they are constantly changing in both directions!