Well, unlike the Facebook and the Linkedin address books the Xing address book only mixes into the Android address book after installing and launching the Xing application. Maybe that’s because the makers of Android have nice deals with Facebook and Linkedin and not with Xing, but it just works a lot different. You can join your various “standard” entries within your Android address book, and the Xing address book entries are not reachable and joinable like that. Instead the Xing app adds a reference from a matching Android address book entry to a Xing address book entry.