There seems to be a lot of pilots, aviation stores, and even magazines having a misunderstanding of the FAA rule 91.21 (b all). The misunderstanding that using an electronic transmitting device is somehow ok in an aircraft. So everyone is jumping in their planes with their cell phones and iPads. Pilots, FAA rule 91.21 states they are all prohibited, and the exceptions (a) and (b) are just stating that NON-TRANSMITTING electronics are up to the PIC or carrier. So if you get in your aircraft with a cellular, bluetooth, wifi, 3-4G, you are violating FAA rule 91.21! Plus, you are asking for a lot of possible problems with your equipment. Yes, and that goes for all you iPad pushing aviators. Ipad requires a bluetooth external GPS, and the programs that are being sold with it require internet, all prohibited. The sad thing is, because us Americans fall to marketing, we don't buy what we need, we buy what the advertisers want us to have. This time they are trying to get you into trouble, or even kill you. There is enough aviation GPSs and EFBs out there that don't require you to break the law, just say no! Flying Magazine you stop pushing them too, I don't want to have to stop reading your magazine, you know better.