I just recently disassembled the innards of a Nokia cell phone and saw that they go to very extensive effort to shield the PCBA inside these things. There were separate cages soldered to the PC board over the RF section and the analog (transmitter/receiver) section, and then the COG type graphics LCD module had its own shielding to isolate the driver chip on the glass from the cell phone RF.

For sure some of this shielding is necessary to make the phone pass the standard requirements for emissions and immunity. But Im going to guess that a good portion of the shielding is there to protect the phone microprocessor from its own RF transmitter section.

Michael Karas