A short while ago I visited the VoIP Security Workshop in Berlin. In the panel discussion, one of the questioners asked whether in 10 years' time, will we still be dialling phone numbers, or will we use SIP URIs?

At one level the question doesn't matter, because most of us have quick-dial directories built into our phones. When I think of all the mobile, fixed and VoIP or IM devices that I use, all of them have a directory of some kind, although it's difficult or impossible to move lists between them.

SIP URIs are attractive because it gives the potential to have one identifier that you could use whether someone wants to call you, IM or email. Your business card could just have the one URI, and this would eliminate the need to have lists of numbers, IM identifiers and email addresses. On the surface it's good to have all those ways for people to connect to you, but people agonize over when to call which number or email address ("Is he at home now? Should I IM before trying SMS?").

Actually I imagine that telephone numbers will be around forever, since it is a very quick shorthand way to make a call. People have got used to the fact that the numbers have a heirarchy of country, area code and even city. Sometimes people infer things about you from your geographical location, even though in these days of virtual telephony and follow-me numbers, they probably should not. A podcaster friend of mine said that because his show comment line starts with US prefix 206, people assume that he is actually in the same place, but of course the comment line is an internet service that he subscribes to, and he is across the country.

Of course some application software has been written to understand only telephone numbers, so some kind of number to URI translation will be needed for some time. But probably the biggest factor is customer acceptance, and it will be a long time before most phone users are ready to give up numbers.