So it may be only 4 years, 1 month, 12 days and 5 hours to 100% mobile phone penetration globally

Ha ha, found a nice website (thanks to Robin who left us a comment) hosted by Mippin, which predicts how long it will take for there being a mobile phone account for the total population of the planet (there is a mobile phone subscription already 54% of the total global population). They do say, using current projections, that we have only 4 years, 1 month, 12 days and 5 hours to that momentous moment ha-ha..

You might want to hop over and take a look at Phone Count.

The little bit of reality check here, is that this includes counts of multiple subscriptions (as does the current mobile phone subscriber count). That is why over 50 countries already have mobile phone penetrations exceeding the national human population - Hong Kong, Italy, Taiwan, Israel etc are already at 130% - 140% and still growing strong. America is at over 85% and will hit 100% soon. But yes, already today, globally 28% of all subscriptions are second or third subscriptions, so we don't really have 3.6 billion unique users of phones, that number is closer to 2.5 billion and another 900 million subscriptions are second or third subscriptions and often also second phones.

Still a good site and service. Lets see how close that 4 year 1 month prediction is - my gut says we hit that moment faster than that   :-)