Speaking of watered down: do you realize that when your friends are really drunk, and being annoying... you can trick them into thinking you are giving them another beer if you just pour water into a "empty" glass of guinness? The little remnant of Guinness at the bottom of the glass and 12+ oz of water mixed together looks like "normal" beer, and if they are truly drunk they'll never notice the (small) difference in taste. They'll puke less this way, AND not complain about their hangover as much in the morning.
Heh... this would be a beautiful part of a thread titled "How to drink like you're Irish"... just put it in the section "dealing with people who cannot keep up with you, but try"