Take a moment to think about how much of your time – at work and at home – is tied up in arranging things. Organising a meal out with friends, for example – you have to agree on a time everyone can meet, choose a restaurant that has a suitable menu, book the table, book a cab home afterwards … a whole lot of tedious and interdependent little tasks. Charles Petrie of the Stanford Computer Science Department thinks we will start using ‘wizards’ – quasi-autonomous web-service software – to start doing these sorts of task for us, by enabling machines to negotiate witrh each other on our behalf. Sounds great from where I’m sitting. But what will happen when those programs make mistakes? Who would be legally responsible for unwanted bookings made by software error?