The hard thing about scaling a service like this is the social graph, AKA. when users have a lot of followers. So I'm going to use the freemium model and let users follow 10 or 20 people for free, and then start charging.
That way I'll start making money at the same time I have scaling problems.
Sure, I'll give a free premium account to anyone on HN that asks. I have a blog over at http://www.maximise.dk/blog but it's boring and there are definitely no posts that are only 14 characters.