I unfollow people on Twitter when I don't care to see what they're posting. Most people don't use the tools that notify users when people unfollow them, so it's not a big deal. Even for the ones that notice, I just don't care. I don't use Twitter for friends; I use it for interests. If you're not posting about my interests with an acceptable signal to noise ratio, you're unfollowed.
Using App.net to filter out people you don't want to hear from won't work unless you think the value of ones posts correlates with their propensity to pay. I doubt that's the case, and you're definitely going to filter out plenty of worthwhile content that people post on Twitter.
It seems to me that people want App.net to succeed regardless of the likelihood that it will solve their problems. This is a good position for App.net to be in, but I don't understand it.