Well, there are several contributing factors:
1) I have been running censuses on a lower number of factions than usual for me since the Pilgrim's Bounty began and spending more time playing specific characters.
2) I have only one account and since I started a new alt a few days ago, my flexibility has been almost eliminated. I am now seriously looking into deleting several of my "permanent" census alts as I will also need more space for goblin / worgen characters after I get my hands on Cataclysm.
3) Also, your 3rd conclusion is faulty... compare Balgair's results from 22nd to her results on the 24th... the drop is close to 10k updates between fairly close days. If, as I heavily suspect, it's related to decisions Rollie made on 24th, we are about to see a massive drop in overall updates... and Balgair can bury her dreams of ever bypassing the records she has set, as they will become impossible to beat unless one can afford to spend time operating 3 or 4+ accounts simultaneously.
As of right now, she has already pushed the monthly new ones to values I did not even believe were possible... and despite the axing of 24th, she already has over 676k updates...
The problem is... the month is almost over and right now... she has 14 unprocessed entries... 837,062 updates is her (and site's) all time record. That means that excluding what she can do today, she needs each of those submissions producing an average of almost 11 500 updates to even tie with her old record.
I am very sorry to say this, but I no longer think she can make it.

4) Have you taken a close look at everyone after us three? The big backlog is messing things up... but as far as I can tell, this isn't going to be a particularly good overall month either. In fact, without Balgair's superb efforts, the overall results would be horribly weak.