"Thanks in advance" is kind of like the no-smoking signs that they changed to say "thank you for not smoking". Normally you thank someone after they do somethin

"Thanks in advance" is kind of like the no-smoking signs that they changed to say "thank you for not smoking". Normally you thank someone after they do something, but by thanking them "in advance", you're passive-aggressively pressuring them to do the thing. After all, you've already thanked them, so they owe it to you.