It’s interesting that Xing, the business social network which competes with LinkedIn has chosen now to launch a marketing campaign in the UK this week – probably something to do with the Adtech trade show on in London right now. There’ll be advertising on some 400 Xing billboards by major London Underground stations, ads in the Metro freesheet and online on at The Guardian, The Times, Sky News, Reuters and MSN Hotmail. Xing has about six million members worldwide and around half a million paying subscribers but till now it’s biggest base has been in Germany, and to a lesser extent, Asia. In the UK LinkedIn passed a million members a year ago, so Xing – which is now a floated company in Germany – has some catching up to do.