I turn off my ereader and also double-check my cellphone to insure that its also off! Its the polite courteous thing to do, as well as a good example to others.
I too think my one little reader probably wouldn't do any harm, but several hundred could possibly cause an issue with something in the airplane's control system. I take along a pbook or magazine for the times I can't use the electronic reader.
When I fly its not just about me but others too, so I'd much rather err on the side of caution.
