Lame and pathetic. And I, unfortunately, am to blame. So with my apologies, here is a long overdue answer:
The cities were originally chosen based on partnerships we had with other weeklies: The Stranger in Seattle, Portland Mercury, etc. With the exception of The Stranger, these did not help build a core membership of smart locals and so they terminated. Baltimore was kept alive because it had the signs that it could become more like Questionland Seattle.
We recently put a huge effort into an update to the site and added many features which we thought were lacking (following questions, people etc.). Unfortunately the effort directed on the technology meant sacrificing efforts elsewhere.
We are based in Seattle which means we have always had two local experts around to make sure questions were answered etc. We cannot play that role in Baltimore and don't realistically have the resources to staff the individual sites with a smart, local person to promote the site, make sure questions are answered, recruit experts and a core membership.
We'd love to see the other sites flourish and would of course appreciate any ideas and feedback on how to make that happen on a budget of effectively zero.
Thanks for your interest and my sincere apologies for the delay. I wasn't aware of the question as it arrived somewhere in a thicket during the Questionland redesign.