I believe that the radiation emitted by mobile phones is harmless.
My argument is not based so much on the scientific evidence—because there isn't very much of it, and what little there is has either found no effect or is statistically dubious. Instead, it is based on a historical analogy with previous scares about overhead power lines and cathode-ray computer monitors (VDUs). Both were also thought to be dangerous, yet years of research—decades in the case of power lines—failed to find conclusive evidence of harm.
Mobile phones seem to me to be the latest example of what has become a familiar pattern: anecdotal evidence suggests that a technology might be harmful, and however many studies fail to find evidence of harm, there are always calls for more research.
The underlying problem, of course, is the impossibility of proving a negative. During the fuss over genetically modified crops in Europe, there were repeated calls for proof that GM technology was safe. Similarly, in the aftermath of the BSE scare in Britain, scientists were repeatedly asked for proof that beef was safe to eat. But you cannot prove that something has no effect: absence of evidence is not evidence of absence. All you can do is look for evidence of harm. If you don't find it, you can look again. If you still fail to find it, the question is still open: "lack of evidence of harm" means both "safe as far as we can tell" and "we still don't know if it's safe or not". Scientists are often unfairly accused of logic-chopping when they point this out.
Looking back even further, I expect mobile phones will turn out to be merely the latest in a long line of technologies that raised health concerns that subsequently turned out to be unwarranted. In the 19th century, long before the power-line and VDU scares, telegraph wires were accused of affecting the weather, and railway travel was believed to cause nervous disorders.
The irony is that since my belief that mobile phones are safe is based on a historical analysis, I am on no firmer ground scientifically than those who believe mobile phones are harmful. Still, I believe they are safe, though I can't prove it.