As a retail worker, I have to say the cell phone. I cannot serve you if you're chatting away on your phone. Blue tooths are the worst.

Very hard. The complete works of Shakespeare, The Witch of Blackbird Pond (always great to reread), Pride & Prejudice, The Three Musketeers, and Atonement by Ian McEwan.

Happened to me many times--very irritating. I found out about the identity of the Face of Boe in Doctor Who on a non-spoiler protected lj post. Grr. An introduction spoiled the ending of Man in the Iron Mask for me. (When x dies at the end of the book...) Also, my brother spoiled the ending of Shrek.