The Bali bombings in October 2002 were carried out that way. And yet cellphones are still legal in Bali resorts. Why‾ Because the benefits of easy, affordable mobile communications - particularly for locals whose cellphones are their chief (if not only) telecoms device - outweigh the risk of another terrorist attack using that particular method of detonation.
Admittedly, this hasn't stopped some governments from blocking cellular services for security purposes. Pakistan and Nepal frequently shut off cellular services to prevent terrorists or insurgents from using them. But such bans typically never last for a simple reason: the benefits outweigh the risks.
Which is a key point for any country: most people who use mobile phones and Wi-Fi are not terrorists. Banning a technology because some people might use it for bad things makes about as much sense as banning sledgehammers because someone could use one to kill you. Besides, it's not as if terrorists will have no way to set off a bomb on an airplane if they're not allowed to bring an MP3 player onboard.
But who knows‾ The ongoing war on terror has resulted in plenty of irrational decisions in many countries based as much on politics and the appearance of doing something to protect the citizenry as countering an actual threat. On the other hand, passengers are more likely to miss their laptops and iPods during a flight than their nail clippers and lipstick. - telecomasia.net