On the topic of poor bottle share etiquette, there is a guy who used to be in our "tasting group". He was/is an obsessive ticker - he sits at shares tasting every beer while simultaneously typing reviews into his phone and conversing with absolutely no one. Besides offering little to nothing as a person, he also went to minimal (if any) effort to bring beers that anyone would enjoy and actually bragged that he was bringing "****** shelf turds" to one of the guy's birthday shares. Not only that, but he would specifically request that other people bring their most prized, rare bottles so that he could tick them.
His only redeeming quality was that he had a strong liver and was therefore a good "mop", thus helping us feel less bad about wasting so much great beer.