Interesting. Taking a look though, it appears they're ranked by the total # of attempts, rather than the # of (different) people who've ridden the segment (eg. Alpine to Kiku sprint has 21,863 people having ridden this segment, or about ~3K more than KC5 ).

I'm maybe a bit surprised a bit that the southbound KC-5 segment is up there, vs a northbound segment but I suppose more riders come back via 9W than head north. Also, I assume a factor as to how long ago someone actually created the segment and that segment has been in existence.