The answer is simple: WE DON'T KNOW. If there is an effect, it is bound to be very long-term, and very subtle. There are so many users out there that the statistics are beginning to look quite firm on this. Even the heart-wrenching story of the tumor 'caused by the mobile phone' is very likely no more than a case of very, very bad luck.
However, I am all for the idea of restricting the use of those dang mobiles: you cannot sit quietly in a public room anymore without someone's technological fetish performing a bad reproduction of a popular ditty. *And* then spending many minutes in a loud voice talking about who did it with whom, or discussing things which really should stay private (loans, medical reports, parole offenses).
