People have crappy short term memory, bad hearing (hitting the clubs too much?), selective hearing, or just aren't paying any attention. It bugs me when they're physically present, but their mind is elsewhere. Generally, I'm not too bothered if we're in groups where discussions can get flowing so rapidly that it's easy not to catch anything, but if it's private (especially if it's important) then they're testing my patience.
It gets on my nerves even more so if they can't read because it's so easy to backtrack to take everything back in. Sometimes, I avoid the debating forum because of this one reason. I'm sure it gets on the nerves of most INTXs who tend to be precise with what they say.
I greatly fear the falling literacy rates with the advent of l33t-speak sometime within the last decade-and-a-bit. It seems that falling literacy rates equates to a lack of listening skills and the total deprivation of face-to-face verbal comprehension at times. Perhaps this is one of the major contributing factors leading constant repetition of the same points and the wastage of energy (the amount of vocal power wasted all these years I could have used to learn to sing or save lives with meaningful speeches).