My pet peeve is some of the people who have their collection/traders as the same book, it's just frustrating when ALL the pins in my book are for trade, but everything I like of theirs is their "keeper" but there's no way to distinguish unless they say that.
I also hate the ones who pick something OE, or with a really high edition size from your book, then pass you theirs and it's all Soda Fountain, WDI, and DA pins, which any of them are no where near the same value of the pin they want from you. You ask if there's anything else they want from you, and they say no. I've honestly responded, well I don't know why you're asking to trade, since you're just going to laugh at me if I ask for anything in your book. They're usually a little off guard by that, and take their pins and go. I think they just want to show off.
Lots of meanies at Disneyland today, and people with books full of scrappers. We chased off a trader who was trying to scam a day guest into buying brand new pins, in exchange for scrappers. We stopped and told the woman what scrappers were. The trader was pissed at us, but they were very obvious scrappers and it's wrong she was trying to scam this woman for real pins.