There's a thread about it here too.

I'm not enthusiastic about the idea of dropping everything for a human mission to Mars.
Such a flight will need preparation and a major factor, as Larry points out, is the time it will take just to see if everything works fine, for the entire duration of a Mars flight.
Can a Mars lander work allright on Mars, even after 7 months in the interplanetary vacuum (which is not the LEO vacuum)?
Can humans perform efficiently on Mars, after 6 months of confinement?
It's possible less energy is needed for Mars than on te Moon, but that's less a factor than the duration of the flight.
The duration also affects the public's interest. Too long and there's less attention, more boredom. Boredom is a dangerous factor for the astronauts too.
Also of all the planets we can see (and even all the planets of our solar system), Mars is the planet for which we must wait the longest time for a next opposition or a next launch window.
While the Moon is right there; seen by everybody on Earth (whil we can see only 5 miles around us at any time) it relates much more to us. It is an airless world like most of all the celestial bodies; it needs a spacesuit just like every other world except ours.
There are plenty of unattractive things about the Moon, compared to Mars, but if we learn how to cope with them, all the other worlds will become much more interesting.

Raoul