2) When an e-mail is not sent for whatever error (user, hardware, software).
3) A failed pickup attempt online with a chatroom companion; rejection
2) A: Did you get my e-mail? It was very important.
A: Crap. The TPS reports are going to be late because of a stupid e-fail.
3)A: you wanna cyber
A: Well that was a total e-fail.
Trying to make up something utterly stupid to post on the internet to impress a bunch of people who don't really don't care to begin with.
A more direct example would be kids with no lives trying to duplicate the 'numa numa dance' to become an e-celebrity.