New people would help a lot. One of the problems is that the old-timers are tired of having the same arguments over and over again. There are only so many times you can write a quality post to a gunbortion thread, and most members already know everyone else's talking points.

My on the Backroom decline:

Bush leaving office 1/20/09. His administration was worth at least one quality thread a day. His "wars" and the other proxy conflicts drove a lot of discussion. Not much hot going on right now, even though there is a lot of cold conflicts and maneuvering under the surface.

Obama taking office and the ensuing media lovefest. The liberal media took it easy on him (at least for a while), while for the most part the conservative media went on a continuous, ugly rant about socialism, with veiled racism on the side, instead of just blasting his policies with decent arguments and good reporting. USA-related Backroom threads at this point changed, with liberals (US version) on the defense while the conservatives went into attack mode, this generally doesn't make for good conversation. And to the last...

US-centricity. It's not that having a very large percentage of USians is a bad thing, but frankly our news media is craptastic and interesting, compelling storylines don't get much play over here. It's hard for us to start good topics if we aren't aware of them. One of the main draws for me in the "old days" was the threads about stuff the US media either ignores, hides, or is just plain incompetent about. AdrianII, Tribesman, etc. used to find stories with all kinds of cool slants to them.

So, yes, I blame the Backroom decline on Obama.