Don’t Press Any Key to Continue

Clayton Miller:

Imagine clicking “send” for an email message and watching your message appear in a brief queue. Perhaps it counts down about ten seconds before sending, more than enough time to cancel an erroneous send, but little enough time in the scope of e-mail communication as to not interfere with normal usage.

Gmail already supports something like this for sending e-mail, but it's easy to see that the same concept could be applied to many other non-undoable potentially slightly dangerous actions.