While it does offer a lot of automation, something bothers me about it.
For my personal Twitter account, I am a strong opponent of "follow spam". In other words, people or entities I know nothing about try to follow my Twitter feed. They have zero interest in what I'm discussing. And that is the point we realize it is a form of spam: they're not interested in what you say, but they will hope you notice they have followed you, and that this will hopefully lead to 1) you following them back, so you get their tweets in your timeline, and/or 2) you see their URL in their profile, and visit their site.
That is why I'm wary of something like TweetAdder. Some might consider it to be spam, as I do. It could bother a smaller subset of users to then flag my Twitter account as spam.
I wonder if software like this is even worth it. Anyone else ever try one of these systems to build a Twitter follower base?