I've read a number of articles in the past week regarding TweeterGetter, most of which identify it as a ponzi or pyramid scheme. At first glance they seem to be right, however I've given this a lot of thought and come to the realization that they couldn't be farther from the truth.
TweeterGetter is basically a multi-level marketing tool to get new followers on Twitter. Yes, it is pyramid shaped in nature and involves you following several people below you in the "chain" in order to be added to the list of those to be followed. That's where the similarity to the aforementioned schemes end. Getting new followers is no guarantee that those tweeps will continue following you. It's up to the quality of your tweets to keep those followers. On the flip side, you can stop following the people who you were "forced" to follow when you joined whenever you want. Joining essentially costs you nothing and the gains are short lived unless you add value to the twitterverse.
One of the great strengths of Twitter is the way it brings together people who would have never otherwise met through their common interests/discussion points. I see this as just one more way you can connect with people you might not have had a chance to meet. Only you can decide if gaining possible followers is worth following a few random people for a bit. If so, give TweeterGetter a try!