Although I completely agree that agave is unhealthy because it is basically devoid of healthy nutrients, I just want to mention that Mercola has started an anti fructose campaign. He thinks fructose is the devil when it comes to health. But in all reality he only thinks this way do to studies done on the human consumption of fructose, however all of the fructose used was a bunch of processed crap. I won't go into details but when they produce fructose for commercial use they isolate it as thoroughly as possible and its just as much crap as white sugar. The thing he never seems to realize is that he supports the regular intake of fruit...fructose is fruit sugar! As we all know fruit is not the enemy here however isolated sweeteners such as agave is.
I've read that Dr. Mercola article, too. He does present some valid points, but vilifying fructose as a whole is definitely contradictory to him advocating fruit-eating. I agree with kurite that refined sugar (including agave) is the real culprit. Only using whole and easily digestible foods is how you can help prevent unhealthy side effects and diseases. I also agree with sv3 that whole fruits used as sweeteners is the way to go. I love using dates (as a paste/syrup the way sv3 describes) as sweeteners in my "special-occasion-only" raw nut-based desserts.