Though tin foil hats do protect you from electromagnetic radiation and from some forms of ionizing radiation, they do not protect you from all possible electromagnetic radiation:
In a not-too-serious-studyRead the conclusion first, it was found that tin foil hats actually amplify frequency bands that coincide with those allocated to the US government between 1.2 Ghz and 1.4 Ghz. Link to PDF with FCC band allocations.
For all helmets, we noticed a 30 db amplification at 2.6 Ghz and a 20 db amplification at 1.2 Ghz, regardless of the position of the antenna on the cranium. In addition, all helmets exhibited a marked 20 db attenuation at around 1.5 Ghz, with no significant attenuation beyond 10 db anywhere else.
The helmets amplify frequency bands that coincide with those allocated to the US government between 1.2 Ghz and 1.4 Ghz. According to the FCC, These bands are supposedly reserved for ''radio location'' (ie, GPS), and other communications with satellites [...] The 2.6 Ghz band coincides with mobile phone technology. Though not affiliated by government, these bands are at the hands of multinational corporations.
It requires no stretch of the imagination to conclude that the current helmet craze is likely to have been propagated by the Government, possibly with the involvement of the FCC. We hope this report will encourage the paranoid community to develop improved helmet designs to avoid falling prey to these shortcomings.
As these bands are reserved for radio location some people might interpret that as brain location...