Sorry, it wasn't 7W/kg. The 'behavioral change' occurs only at 4W/kg: "“The FCC limit for the head (SAR of 1.6 W/kg) is just two-and-a-half times lower than the level that caused behavioral changes in animals (SAR of 4 W/kg),” says the representative. “Thus, the brain receives a high exposure, even though the brain may well be one of the most sensitive parts of human body … and should have more protection.” http://www.wired.com/gadgetlab/2009/...one-radiation/
In general, the lower the SAR the better the phone, from a potential health hazard point of view. For instance, Apple’s iPhone 3G has a maximum SAR of 1.39 W/kg when held at the ear.