Many of us travel a lot. This means high roaming charges and no local phone number in the country where you are. Some people yet decided to buy local SIM cards and put them in their cell phone whenever they arrive at the airport. For them Truphone has just presented their new Multi-SIM capability, which supports travellers who take international SIM cards with them abroad. Calls to their Truphone number will reach them whichever SIM they're using at the time.
That's nice, but even cooler is Roam4Free's "Get a local fixed line number for any one of 28 countries on your SIM". Instead of exotic numbers from Estonia, Liechtenstein or the Isle of Man they will point local fixed line numbers for any one of 28 countries to their SIM cards when the new version of Roam4Free comes out. The customers can then be called on mobile phones with a local fixed line number.
Local numbers for global SIMs seem to be the new trend. The German company GlobalSIM has also started recently to give local fixed line numbers from 43 countries to their SIM card customers. That's even better than Truphone's Multi-SIM capability. But I see the disadvantage that this call forward will surely cost extra and the owner of the mobile phone has to remember many local numbers.
So I think that an entire new number range is missing for worldwide mobile telephony. The best thing would be a cheap interconnect to the ++882 or ++858 number range, or something similar. These are international codes that don't belong to any particular country, but to ENUM services. It would be great if people could call them from every country for local prices. So you would never have to change SIM card or number for travel. You just had a virtual number, similar to German 032 numbers which don't belong to a particular city but to VoIP.