Gore-Spattered Heavy
Currently, to trigger RTV it takes 12 votes. I assume this is because most servers used to hold only 24 players and so 12 was a reasonable amount. But now that most servers are 32-player, it only takes 37.5% of players to RTV. This is a problem mainly because now maps hardly ever run for their full time limit. On the server I frequent (Payload US+), maps average about 3 rounds before switching. Doesn't matter the map. So on multi-stage maps like Goldrush sometimes players spend the whole map on the same team. And no one ever picks "stay on current map" when we RTV because it's seen as throwing away your vote.

Another--albeit much rarer--reason this is problematic is because it makes RTV wars easier. When Hoodoo was added to the server it cause a huge uproar from a vocal minority. The very first time we got to the map, we immediately RTVed out to a different map. In response, when we got to that map it was also immediately RTVed out of and back to Hoodoo. Since it only requires 12 out of 32 players and people tend to blindly agree with the vocal minority, all one has to do is say "let's RTV" over the mic and that's usually all it takes. It should take 16 votes, at least half the server, to trigger RTV.