The thing that bothers me about this is that the emphasis is on masts. Electromagnetic radiation follows the inverse square law, so you'd be wiser to worry about equivalent transmitters that are much closer - say, against your ear, for example. Masts pump out a signal that has to reach phones, despite its attenuation. Equally, the phones have to reach the mast. I'm not saying that they're the same power, by any means (a phone is working from a battery, while a mast is plugged into the National Grid, for starters), but really: forget wi-fi (which has to reach to a nearby room and is on your desk) and worry about the phone (which has to reach a block or so, and is at most two inches from your brain.
There is a difference between masts/Wi-fi base stations and phones/wi-fi laptops, of course: you choose to have the latter, while someone else inflicts the former on you without you knowing.
Personally, I think the technology went the wrong direction here. I think that phones should be working more like wi-fi: they should first try to connect to a low-power local cell (using BlueTooth levels, if plausible), before cranking up the power and reaching for something further afield. There are benefits: battery power would be longer, local cells could route over fibre instead of EM spectrum (meaning greater privacy, shared spectrum), less interference (so easier to certify on planes, etc.). And local cells could also interrupt calls (imagine a theatre where the local cell refuses to put through any calls during performances). There are problems too, of course (would you trust Starbucks to route your phone conversations?) but we're getting those kinds of problems anyway (cf RIAA and other corporate intrusions into the communications legislative infosphere). I'm sure it's worth it to have your mobile act as a wireless handset to your landline while you're home. :-)