You alluded to one danger of ignoring culture: that your company will develop a culture that you don't like. However, there's a bigger concern when you ignore culture - the possibility that your corporation develops multiple cultures, which conflict with one another.

You're already starting to define responsibilities and divide the work accordingly. That's good. However, you need to make sure that there's still a lot of communication between the groups, and not just between the group leaders either. Otherwise what happens is that people get isolated in their own group and begin to think of other groups in the company as the "other". Things only go downhill from there, as these divisions slowly drive the groups into working at cross purposes.

The real job of company culture is to remind employees that they're all in business together; that its not their group against the other groups at the company. If your culture manages that, then it almost doesn't matter what sort of culture it is.