Let's not mince words: Wikipedia administratorship can be a serious liability. The 'reward' for volunteering for this educational nonprofit can include getting one's real name Googlebombed, getting late night phone calls to one's home, and worse. The Wikimedia Foundation has never sent a cease and desist demand to the people who have made a years-long hobby of driving its administrators away.
It is hardly surprising that, in this weak economy, wise editors have been declining offers of nomination.