One of the worst things I see young girls doing these days is caking on their makeup. They have probably heard that "less is more" but do they listen? No.
The second thing, is people who don't blend their foundation down into their neck. It's an unforgivable misdemeanour in my eyes. Why would you put on a whole face of beautiful makeup, only for it to be ruined by the obvious line at your jaw?? Grr!!!
There are plenty more, but I risk being in a bad mood for the entire day if I continue!!