I composed this query on SEDE the other day: Meanest users (users by ratio of downvotes)
If you look at the data displayed there and compare it to the current information on their profiles, you'll find that many of their downvotes simply vanished. Enter a mininum of 100 downvotes. GEOCHET's profile shows s/he has 1840 downvotes, while the query says 3412, a difference of 1572.
The data on SEDE is only a couple of months old, so I think it's highly unlikely that this many posts have been deleted since then (and that's not taking into consideration that fact that these users have cast more downvotes in the meantime).
So what happened to everyone's downvotes?