How to give everyone a headache!
Whats the name of that website again? Oh yes its theregister..
OK, guess ill try .co.uk first, then maybe .com if that doesnt work.
But now, it could be (or soon to be if this trend continues:
theregister.<insert one of a thousand other words here>
Obviously using theregister is a bad example as its an established site and everyone knows its extension, but what about newer sites youve been asked to checkout but the person telling you cant remember the extension?