I could have sworn we were over 90,000, and now we are 87,300. (I am going by the count on the Leaderboard.)
(Not a big deal, of course, but I am just curious.)
Immediate edit: Were private accounts dropped from the leaderboard count?
Yeah, there were zero-activity dormant accounts that I dropped a while back. I probably should have been doing something more useful with my time. 
Oh, man, those accounts were artificially boosting my percentile ranking. 
How long does an account have to be dormant before it gets cancelled? I’m up in Alberta and the winters can be severe. Plus, I am in a rural area so new streets are only possible when I am out of town.
I can’t speak for James, but he did say zero-activity dormant accounts, so I’m guessing your account is safe even if you have to take a long hiatus.
Yeah, it’s also not an automated process - I was just feeling spring-clean-y on a random day. There were zero activity accounts that hadn’t visited in something like 5+ years.
I don’t currently have plans to remove dormant accounts.