As both my private and my business life is pretty international I would estimate that 80% of my calls are international these days. Most of these calls are carried over VoIP for some of the distance. Interestingly, that has some strange consequences for the phone number that the other end is shown. Some examples:
Business calls: I use a SIP VoIP client on the PC and the SIP network of my company for most business calls. To reduce cost, my company has a lot of voice gateways deployed in different countries. The IP network thus transports the VoIP call to the closest media gateway and then releases the call to the public circuit switched network. As a result the caller always sees a local number instead of my real number. Nice to hide the fact that you are not actually in the country. However, the number can not be called back.
For private calls I use Skype a lot. Skype does similar things and has gateways in many countries to release the call to the public telephone network as close to the destination as possible. Again a mysterious local number is shown (e.g. +491234). Most people are quite surprised to see such a number.
When I am in Germany and have to call a mobile phone abroad I use one of the many alternative PSTN operators. Again the number that is shown looks funny and has nothing to do with my real number.
And when I am out and about and want to call abroad from the mobile I use the services of Rebtel which lets me call a national number and then forwards the call internationally at a fraction of the cost of a direct call from the mobile. Again, same story with the calling number being displayed on the other end.
So why is there a number displayed at all at the other end if it is just fictuous? Nobody ever heard of CLIR?
P.S.: I wonder if there is a law prohibiting media gateways in a country to send the international number from a different country!?
P.P.S.: For the moment I seem to be the exception. So most people these days pick up the phone and say: "The number looks funny, this must be you, Martin!". Sort of an alternative caller ID...