Larger companies have an advantage when it comes to the issue of headcount for supporting communities--it is called "voluteerism";) Seriously, the Channel team doesn't technically have asigned headcount to channel community program, but it does have over 100 volunteers. Like any good volunteer they have a few key attributes: they are passionate, busy but willing to spare a bit of time for a good cause, generally intelligent and collaborative (i.e. problem solving as a team). In fact, we have noticed that the more volunteers (sometimes heavily coerced volunteers;)) the less time required of each person (with expections = community managers).
Additionally, there is a specific and critical role that some employee volunteers can play, that of the "information broker". The are not knowledge experts, but they are people experts. In fact, we have found the health of the community primarily relies on a reliable team of "deputized" information brokers. There job, once trained, is to monitor and "broker" discussion and problem solving activities in the community.
Thanks to the features in clearstep (alert me, emails, embedded links and pdf's of discussions) it makes it incredibly easy and time efficient to play the role of an information broker.
Hope these ideas help a bit. For more details, don't hesitate to contact me.