One of the other benefits of this kind of approach is that it allows the two sides to inform each other without hindering each other. Each function gets the proper space to "breathe" in a sense.

For example (and this draws entirely from my own anecdotal experience), I find that in the course of marketing, I often get the best feedback/inspiration from users/community members, and this is very helpful in deciding what to implement next. However, I find that this pseudo-research process is only effective if I take enough time to process the information in whole. In other words, if a user has an extremely compelling idea, it can be tempting to implement it right away. If I resist and take my time, considering the idea in the context of the dozen other points of feedback I've collected, I can often distill the jumble of ideas into a stronger, singular feature. If I jump in right away, I'll inevitably end up in a state of feature creep.