My opinion here is that while a link between cell phones and brain cancer cannot be ruled out, without a strong correlation and a numerical statement about the odds, it seems very unlikely to me that such a connection is something to worry about. I’m far more worried about the dingus in traffic in front of me gabbing to his friend on his phone and causing an accident than I am about me getting brain cancer from my own.
I was going to write a blogpost about this myself, but then I noticed this post from Phil Plait (aka @badastronomer on Twitter).
I couldn't have said it better myself, don't forget to check the reference links in the post as well.
FYI: there is continual research on this matter, not just from gov't funded organisations, but also the operators are researching this. So far, there is no indication that mobile phones have any effect (at all) on humans.
Ok, maybe they do. Some of them seem to become complete idiots who think they can call/text during driving...