Mobile health scares
Mobile health risks: "The real dilemma is deciding whether mobile phones constitute a real threat like cigarettes or an imaginary threat as per the radiation threat to pregnant women from VDU screens in the 80s."
Very important, particularly given the high usage of mobile amongst children (though whether they're actually high users of voice - which is presumably the most risky activity - is a different matter, I've not seen the figures).
One of the scenarios outlined in Wireless Foresight (one of the 4 or so books I'm currently ploughing through) is exactly this: a health scare sets the mobile industry back by 5 years or so, leaving the public reticent to use mobile and forcing telecomms businesses to re-engineer much of their infrastructure in order to reassure their customers.