I started re-reading (I'm sure I read it the first time) this thread from the beginning, and was amused by the inability of most posters to understand the simple instructions in the original post—or to even understand the title.
I think that people just don't give a damn- when I see these kind of whimsical threads with 'rules' I am more tempted to break them. And when I see the OP trying to moderate their thread.... I think I am not alone in wanting to cause just a little bit of keyboard-rage.
Another peeve I see is the disrespect of some tourists in foreign countries towards the locals. Depending on the country, i think this qualifies as a safety concern.
One more peeve is unrealistic expectations either underwater or on land. The backpacker to 'flashpacker' phenomenon where more and more people expect conveniences like hot running water 24/7, electricity 24/7, wifi, cable TV etc. in these far-flung places around the world. Rather than going out and getting dirty, they sit inside and blog about their cultural experiences based on reviews on the lonely planet forum. Underwater they want mantas, turtles, dolphins and whales but in 30 degree water, 30m viz, zero current, within a 10min boat-ride from the hotel because they feel queasy on water.