If you join an official public server, there's an extremely high chance you'll join with cheater bots that spawn endless, aimbotting snipers. It's less of a problem on community servers as they're actively moderated by players, but official servers have to rely on vote kicking a fresh cheater bot every few minutes.

This is all done by some script kiddy group who apparently want to highlight Valve's deprecated support. Basically ruin the game until Valve fixes the game. There's also some measure of farming ingame item drops to sell for money, I think.