Stormy Peters reflects on where community managers ought to reside in the corporate structure. According to Bernard Golden, community managers ought to be in the support structure of a business. I've heard sillier things, but I'm not convinced by a long shot.
Right now, most of the community managers I know (and it's a rapidly growing field, I didn't know any "community manager" types when I started working in the open source market in 1999) work in either marketing or engineering. The problem, of course, is that community management (whatever it is -- few people agree) doesn't fit precisely into either of those areas. It's probably easier within smaller companies that have a flatter organizational chart.
A community manager can "live" and do well in either group, but the group you're in obviously tends to influence your objectives and what you spend your time on. If you spend your time working with and being managed by engineering types, your objectives won't look quite the same as if you were working with and being managed by marketing folks.
The idea that a community manager should be in support, though... I guess that really depends on the company. In my experience, the support group would almost certainly be the wrong group to work in. Support, in my experience, spends its time mired in problems with the company's products. It might make for a good perspective for a company that has focused on building a strong user community -- but doesn't put the community manager in a good place for working with a developer community or putting in place the tools that contributors (and future contributors) need to participate.
At least I hope we can all agree that the community managers don't belong in sales...