So I checked Johann's historical tweets today to check my sense that he had been tweeting less this year than last year. I didn't include all retweets or all answers to other people tweeting @ him, but roughly:
(The Jan # is through the 10th, as to be fair)
1) Absolutely meaningless.
2) He's just busy. In August one of the admissions staff members left NU and he tweeted:
She's also been my twitter conscience for the past two years. I fear for what might happen.
Maybe it had a big impact.
3) All the activity in the NU thread last year made them hyper-aware of being watched and wanting to communicate with those kids.
Anyway, just something I noticed. Maybe less applicants just means less questions overall for him, or more people are doing their research, or a personal preference on his part.