They are up to 10 now But yep, it was made by 9 people originally.

Personally I think the small team at ironclad did an amazing job and frankly this is one of my favorite games.  It must be double the satisfaction for the deveolpers since they made such a great product with 1/10 the size of some game development teams. 

I remember Blair did an interview at one point and he said (to paraphrase) that whenever you have people whose only job is to manage other people, you're already too big So that's their philosophy and the kind of company they want, small and where everyone is involved and there's much less red tape, so to speak.

Last time I checked they had posted a job opening for a concept artist, so maybe they even have 11 or so by now! Or at least looking to get a handful more people.

Aside from the idea that more staff means more people-management issues, from a software development perspective, it really starts to get complex. SVN starts requireing serious check-in rules/policies, test and debug complexity increases, chances of missing a development issue gets higher, code review becomes more critical, etc etc. Just look at the complexity of softare development at Microsoft or Linux Kernels and you can see that the process (not talking about quality) of software development is really complex.