I definitely follow these rules in high impacted areas. In some very remote off-trail areas where less than a handfull of people visit, I have camped closer to water sources. BUT, I ALWAYS wash and do #2 200 feet or more from the water sources. I have camped on the top of glacial polished flat rocks that happen to be right next to a lake or stream. In this case, you have to be aware of everything you do so nothing gets into the water. So it is a matter of good judgement. There are some very over-used places that I, like OM, get more than 200 feet away. The large 2+ gallon collapsable water jugs are very useful for expanding your campsite possibilities. The "rules" are really guidelines- sometimes you need to be even more distant than the "rule" says. And for flooding- the flood prone area often has residual flood debris on the ground. If you see lots of this, then get up higher! Also watch out for dry gullies that flash flood. Every year you hear of unlucky campers who get washed away at night. When you pick a campsite, ask yourself; do I see any tress that would fall on me?, do I see any flood debris?, am I under an unstable slope?, will a rock fall off a cliff and roll into my campsite?, am I protected from high wind?, is my site robust (not fragile-- walking around should not create footprints), and yes, in a well used area are you 200 feet from water sources.