I notice a weird (well, according to me) thing about passwords. For example, if I type an incorrect password during login, there will be a few seconds' delay before the system tells me so. When I try to
sudo with a wrong password I would also have to wait before the shell says "Sorry, try again".
I wonder why it takes so long to "recognize" an incorrect password? This has been seen on several distributions I use (and even OSX), so I think it's not a distribution specific thing.