Hey Seth,
A lot has been said lately with Radiohead's recent tour about the ecological costs associated with major tours, particularly at large venues outside the range of mass transit. Recently, I bought tickets for an event at the Charlottesville Pavilion and after selecting the number of tickets I wanted, it offered me the ability to buy a 40cent CO2 offset credit for each ticket, if I chose. It's not a full-scale answer to the environmental questions being raised, by any means, but even the opponents of the CO2-credit system admit it does afford some help (along side the push for car pooling, etc).
I know VFest and Merriweather both pride themself on their green-ness and trying to preserve the natural environment as much as possible. Would it ever be possible to have a similar opt-in system for CO2 offset credits for IMP shows held away from the 9:30 Club, or does ticketmaster make it impossible? Has there ever been any thought to building in money to the ticket cost (like some places charge a "facility fee" in addition to the ticket, well, in this case, an environmental fee), or is this perhaps already happening?