There's yet another agenda that at this point might be the thing that keeps the Cantab's open mike nights going: musicians socializing with other musicians. Many of us are working so hard that it's difficult to find a bunch of us together in one place. But it's good to get together and compare notes (as well as rests). If a not-yet-fully-developed musician takes the stage (there were damn few last Monday night--the roster leading up to the McGee and Martin included fully developed ones like Ray Chesna and Ellen Groves), it's actually a good thing to have a noisy bar nearby to cover our own lapses as an audience as we socialize and/or do business with one another. For a developing artist, the only place you can get better feedback is on the street, where the only people who listen for long are the ones who are enjoying the act. If you get silent attention from most folks at the Cantab, you're doing very well (as did McGee and Martin, who were astonishingly good despite the aformentioned handicaps). If you get the attention of the whole bar, including those folks who have other things they'd rather be doing, you're doing very well indeed.
Like frequent Boston Globe correspondent Scott Alarik, and like Ellen and her musical partner David Fishken, Geoff, who has been astonishingly good himself for many years, is providing the musical community an incredibly important service by doing a relatively thankless task. More power to them all.