So, there's another meme going around the geoblogosphere - the top 10 things every geologist shoould know. But it's one of those "think up something utterly unique" things and I'm way too late. So I'm borrowing Silver Fox's idea and changing it around a little: what are the top things that you wish the general public knew? Here's a few of mine:
1. Just because something is natural does not mean it is stable or permanent. If you've got steep cliffs made of relatively soft material, they will be eroded. Don't build your house directly on the edge of such cliffs, especially if they're, oh, in an earthquake-prone area.
2. Natural resources, such as oil, are not infinite, but they're also not totally easily accessible either. When folks talk about "peak oil", they're talking about economically/technically extractable oil. There's a ton of oil/coal/whatever still underground; the issue is whether it's at all feasible to get to it.
3. There's lots of different "bad effects" on the environment. You have loss of habitat; production of CO2 and other greenhouse gasses; contamination of air, soil, and groundwater; species loss; humungous anoxic dead zones out in the ocean; accumulation of trash; etc. The culture and media are obsessively focused on climate change/greenhouse gasses right now, but some solutions for one problem (using minimal gasoline) involve creating another problem (more battery disposal issues).
I'm sure you can think of some other biggies...