Consider Bay-Net in the San Francisco Bay Area. It's increasingly one of the more popular amateur radio groups in the region, with a popular linked analog repeater system and D-Star node. Bay-Net has no members; if you're on the email list, you're in the group. Bay-Net doesn't hold regular meetings, except for a once-per-year gathering at which goals for the coming year are set forth for consideration and an informal expo is held where members bring in projects to share and discuss. There are three "board members" (required to maintain the Bay-Net vanity callsign WW6BAY) but they're not treated any differently than anyone else and most of them group doesn't even know who they are. We host a Field Day site every year and usually come in last place because we spend all of our time playing around with radios and gadgets instead of making contacts, but we always learn something. There are no dues; if we need to buy something we ask for donations and people step up.
One of the great things about Bay-Net has been that it's attracted a lot of younger operators, which I credit in part to the "not a club" approach. I encourage you to consider whether your club might be more efficient, more effective, and more inviting if it wasn't a club at all.
Update: As if to yet again validate this idea, I received an email from a local club that allows non-members to monitor their mailing list:
We are having an election to make a change in the By-Laws. The proposed change is shown in RED LINE in the attached petition and adds the words "more than once" to the end of Article IV, Section 1 of the By-Laws. In essence the proposal is that the By-Laws be amended in order to allow officers to serve up to two one year terms in a row rather than only one term as presently provided. It would not extend officer terms and all officers would still stand for election each year at the April meeting.Gaaahhhhh.....
Update, Part II: I keep getting comments (here and on my G+ post) about the importance of f2f interaction and why clubs provide that. Let me clarify: I'm not saying that Bay-Net never interacts f2f. We meet up all the time, for a variety of reasons. We just don't do it *formally*. If we need or want to meet, we do. What we don't do is waste time with minutes, financial reports, committee reports, voting, etc.