Deleting that drunken message
Apparently lots of people get drunk and send emails or texts that they later regret sending. With these technologies it is very difficult (almost impossible) to stop it being received (with "hilarious" stories as to how they prevented the person from checking their inbox) as it is lost in "the system". "The system" is what makes it so rwopobust, but it's also what prevents you from being able to stop emails.
On other sites that provide a PM feature, though, there is no system for it to get lost in. It sits on the server until the person receives it. Still there is no ability to delete the message once you have decided you didn't actually want to send it though.
