Full disclosure: I backed the project.

I think it's fine if marketers use the service. It's similar to Twitter in that you can choose who you follow. The difference is that if I want Coke in my timeline, I have to follow Coke (or someone cleverly disguised as not Coke) in my follow list.

If companies add their brand to app.net, fine. If people opt-in to follow those brands, also fine. No harm to everyone else.