DANDR cautions not to "overheat" olive oil when cooking, but doesn't say how hot "overheating" is.

So I googled, and found all kinds of hits, including some claiming that if you overheat olive oil it puts out "TOXIC FUMES".

I found <a href="http://www.marksdailyapple.com/oil-fat-overheat-smoking-point/">this</a>, which was somewhat useful, but <a href="http://www.goodeatsfanpage.com/CollectedInfo/OilSmokePoints.htm">here</a> is something better.

Basically, you don't want to heat your oil to the smoking point. If you have recipes which call for high heat, as I do, you'll want to use virgin olive oil instead of extra virgin olive oil.