I'm working on a term paper for my Business of Health Informatics class. This question cropped up while I was writing the paper. My answer is fairly simple: it depends. The developer writing straight forward middle-tier database access code, or implementing the service layer, or the user interface probably doesn't need (but might benefit from) informatics training,
However, the designer and architect would certainly benefit from it.
So, is it an informatics job? No for most. And yes for some. In general, I would say about 2 or even 3 orders of magnitude more people writing Health IT software would answer no.
What do you think?