A new website, called Rent A Friend. Enough said. Well, not quite enough, as I suggest at the Guardian's Cif. A taster:

All friends like to be useful. You're only too happy to feed your friend's cat while they're on holiday, or to help them when they move into a new flat. You offer the help as a gift. It's elicited by the quality of the friendship. They, too, will offer you gifts in return.

But help with the cat or flat is very different from offering you a service. Services are not elicited, they are advertised, ordered and bought. If a friend treats you like that, you rapidly cease to feel useful, for you've already started to feel used. Feeling useful is a means by which friendships flourish. Feeling used is a means by which friendships end.