I've been dabbling in Facebook recently for a number of reasons -- primary among them is that my teenage daughter wanted an account, and I want to know the terrain of any place my kids choose to wander. Now, of course, I'm hooked.

There are so many extraordinary aspects to these increasingly sophisticated social network tools. And I've been pleased to find arts organizations claiming territory and trying to connect in this environment.

But what struck me this week was the extraordinary opportunity and challenge of marketing in these social spaces. In the old days, we considered ourselves sophisticated if we targeted a brochure mailing to a specific ZIP code, or if we attempted to cross-sell a second event to audiences that had already bought another (''You like STOMP? Why not try Savion Glover?").

Social network systems offer an exponentially more nuanced and complex palette to choose from. Now, in addition to geographic location, you can target by almost any interest or affinity you choose -- groupies of the Dixie Chicks, gun enthusiasts, cross-stitchers, sports fans, married or single, high school or college, CEOs or entrepreneurs. It's almost a tyrrany of choice.

As I attempted to create a Facebook ad for my MBA program (just for fun, not yet posted), I had to ask the question: what are the most effective ''proxy interests'' for my potential audience? I can't say ''people prepared to consider an MBA in Arts Administration.'' Instead, I have to think of other values, affinities, or attributes that would tend to include my likely audience, and tend to exclude the unlikely.

Given the low cost and easy cost-control of these small ads, and the ability to target a specific geographic area of users, more and more arts organizations will likely be exploring them to share events and build awareness. But all of them will need to consider the proxies that define their potential audience. And that's a path to marketing that most of us haven't yet considered.

So, what social markers best define the group likely to care about you and your work? If you haven't wondered, wonder now. But be cautious about the assumptions you bring to the table.