Here is a video that just came out from a researcher at a world renowned cancer research center who is warning the same thing.
No one is yet sure what problems might occur (but I suspect in 20 years there will be a sharp increase in brain cancers), so the advice I give to everyone I have a chance to talk to is:
Use your cell phone (and silly looking bluetooth thing) sparingly.
UPDATE: If you need more convincing, here are some tips on what to do to reduce your cell phone risk.
