EDIT: The obvious retort is "what about microwaves?" After all kitchen microwaves operate on the same frequency as your home WiFi. Your desktop microwave acts not by harmonics with the rotational frequency of water, a common myth, but by that that effect I mentioned of smaller frequency back-scattering and thermal agitation. Your counter-top microwave emits 1kW of power into the food put inside it, which is 100-1,000x as much as your cell phone antenna puts out. And it does so inside a closed cavity instead of an omnidirectional antenna. At that power and with full absorption, thermal effects are no longer negligible.

That's why, for example, technicians working with cell phone tower and microwave antenna installations turn off equipment before standing near the transmitter. They do take proper safety precautions. But the concern here is cooked meat, not some abstract radiation or bio-poisoning thing that will cause cancer 10 years down the line.

The concern over cell phone radio emissions started in part due to the large amount of anecdotal reports from those technicians of insects suffering die off near transmitter stations and migratory birds flying straight into the things, killing themselves. But we shouldn't be surprised -- these insects and birds have large organs meant to sense magnetic fields which operate as crude radio antennas, making them actually sensitive to the EM radiation being put out. But this really isn't any different than, say, deer getting trapped by bright headlights on a dark road, and we shouldn't take it as evidence that the same mechanism might be affecting human beings.

Then again, if you for whatever reason have a conductive surgical implant anywhere near your head or pocket, I wouln't suggest using a cell phone or laptop (on your lap). The concern is not great, but that does put you in the same situation as those insects and birds. I wouldn't be worried about the devices used by poeple around you though (1/R^2 laws and all that).