Yeah, I'm with you on the not-understanding-the-logistics part. Shared circles are static content, it's not like everyone's circle is growing as this floats around.
e.g. the guy who was added third is getting added to a bunch of people's circles, but is only following two new people. The gal who's added as person 4000 is now following 3999 new people, but probably won't see many new followers since the thing's probably petering out.