That represents 476k 'micro' subscribers in one year, 277k 'small' subscribers, 151k 'medium' subscribers. Cheapest business plan (bronze) would require 133k; most expensive (platinum) would require 16.7k subscriptions. Github announced 1 million users on 21 September 2011. I can't find any details about current #s or the % of paying users.
Remember that all these numbers double if GitHub only has 20% net profit (bear in mind this would be 2.5% higher than the insurance industry, which is an extraordinarily predictable and profitable industry, and oil/gas, the most profitable industry, sits at 25%).
So while not 'spectacular' it's not at all obvious whether they can generate the sales required to generate the return necessary, and the optimistic attitude of people posting here without any numbers to support their conclusions is a bit disturbing (not a reflection on parent's comment, but in general).
Looking at the numbers I'll make the following observations:
- the total market size of potential GitHub users has a fairly low limit (somewhere in the 10s of millions I would guess)
- GitHub has some popularist advantages but ultimately competes on price as far as I can tell (I've started moving to Bitbucket because I see no point in paying for something I can get for free, and the recent hack shows GitHub doesn't offer better security AFAIT); as soon as they gain a larger market share there's no reason to believe competitors won't want in on the action, and as GP points out, switching repository hosts is really easy
- while it looks like they'll be able to generate that 2% return over the next few years I'm struggling to see them generating a much more interesting return based on the numbers I'm looking at
- I have a feeling people are confusing feelings of "GitHub is cool and I like it" for implying that "GitHub should do well as a profit generating business for its investors"; they are also probably fantasizing about having $100m invested in their own startups and taking criticism as personal attacks on this 'plan'