People I know pay money to get unlisted numbers, take their names of telemarketing databases, get domain registrations which hide their details behind an agent. Others get multiple sets of emails. One for their public face. Another for their friends and associates. How many people can send a text message to Barack Obama’s cellphone? How many people’s cellphones can Barack Obama send a text message to?

Most of us acquire an online identity over time, consisting of our contact details and such attributes as can be pulled together. Ordinary people have relatively little defense against the creeping advance of database builders. But it’s safe to say that what distinguishes the rich and powerful from Joe Ordinary is their ability to control information about them. In some sense being invisible is the ultimate luxury good.