On the Internet, nobody knows you're a dog

On the Internet, nobody knows you're a dog
Originally uploaded by cyberchase.

Wikipedia has a good article about online identity which references this famous New Yorker cartoon

'Online identity is far more malleable than "real life" identity; the latter is shaped by factors that are difficult to control (including race, class, occupation, and level of educational achievement). By means of online identities, people are free to redefine themselves as they wish. (In Peter Steiner's famous New Yorker cartoon, a canine computer user says, "On the Internet, nobody knows you're a dog.") '