I’ve noticed an increasing number of messages arriving with ‘Sent from my Blackberry/iPad/iPhone/HTC’ or similar at the end.

Now I think I know what the official purpose of these tags is.  It’s to explain to the reader why the message may be lacking the usual signature, and be terser than usual, without a salutation or other padding, and to excuse typos.  But let’s face it, part of the point is to crow ‘I’ve got an iPhone (or whatever) – bet you haven’t!’  It’s a bit like the ‘Baby on board’ stickers on cars.  Of course, there’s nothing to stop you putting one of these tags at the end of a message if you don’t have the equipment in question but would like people to think you did.  (Just be prepared for them to ask to see it next time you meet!)