Absolutely, a large site can be done with few people. My company built and maintained fortune 100 sites, and worked in industries from energy exploration to cancer research. We never had more than 20 employees.
Doing it professionally, in my experience anyway, has been a different critter than the volunteer sites I've worked on. In the professional world, you have a contract or mission statement of some kind, and you can hire another person if the works stagnates or becomes unscalable or otherwise has to be reworked from the bottom to the top.
I have faced two things doing non-profit sites. The first is that there are rarely many technical people who step up to do it, so you usually have one or two people on a team who have the knowhow to do stuff like push and pull from database, what recursion is, internet compliance standards, how to both prevent and fight a denial of service attack, etc. Over half the folks wind up being non-technical, and generally the people you are reporting to are as well. Whats more, many of those folks don't understand the possibilities and challenges, so have to be educated - and many technical folks don't want to bother with that or don't necessarily have the people skills to do so. So you get one person who winds up being the go to guy and has to manage it and act as go between, or else do the lion's share of the work himself.
And that leads to burnout when you aren't getting a paycheck and the projects become long and arduous, and they will be at points on the site in question if the ball is getting moved. Or, it can lead to stagnation where one person winds up for years being the go to person, and they are naturally protective of their work and resistant to large changes as the years go on.
As I see it, the GL site doesn't just need to be maintained. And not just designed and coded. But the committee itself needs to be organized to steer clear of those pitfalls by organizing itself to be temporary and systematically turn over people. Otherwise you get bursts of activity and updates followed by lulls.
I've been that guy who has caught the lion's share of the work, or the only technical guy in the crew who can explain the stuff, and I can tell you that once you get yourself into that situation it is extremely hard to chart a path out of it. Its for that reason I'd strongly urge anyone who has something to do with the effort to insist on a very specific mission statement as well as an exit strategy. Both for your own sanity and for the good of the project.
Sorry to ramble :12: