I know I've said this before, but every commercial flight with more than a few dozen PAX is very likely to have an active mobile phone on board - most will have several. PAX can be silly, careless or forgetful and I'll happily lay a penny to a quid that sometimes flight deck and cabin crew can be too.
So, there are only two real possibilities:
(a) there isn't really a problem with handsets, it's just a scam to maximise the revenue from air phones; or
(b) active handsets pose a potential safety hazard on board an aircraft.
If (b) is true then we can never eliminate the possibility of an active phone on board by simply issuing instructions that all mobiles must be switched off (including those in the hold!). We either need a foolproof system of scanning for active phones (tricky because they can be 'quiet' for minutes at a time) or we need to 'harden' aircraft systems so this ceases to be a threat (with the obvious difficulty of retrofitting any required changes).
It's interesting that "Connexion by Boeing" offers Wireless LAN (802.11) operation inside aircraft, which has very similar power and frequency characteristics to mobile phones. Have these aircraft been suitably 'hardened'?