It’s the internet world now, so you can speak to anyone anywhere in the world — right? Blog away, and every Tom, Dick and Harriet from Anchorage to Cape Town can admire your wit, marvel at your wisdom and might even offer a comment in return. Sign them up to your Facebook site, where you can now boast 300, 500, 1,000 friends. But how well do you really know all these people? Would you really respond with a cheque for £50 to an e-mail plea from one of them? OK, OK, I know a surprising number of people get hoodwinked by 15-year-old Nigerian spammers on a cranky old village internet connection, but I’ll warrant that most of you aren’t so gullible — and it’s precisely because you don’t treat everyone on your Facebook list as equally worthy of interest. The bottom line is that our social worlds are actually very small. It’s easy to add friends to your social network site (or SNS in the trade), but it’s another thing whether you’d really lay down your life for all of them. The ...