IMHO there are several reasons why this is not so good idea. First problem is the cost. And I'm not talking about the cost of sending them to Mars, I'm talking about keeping them alive. AFAIK they would require constant supplies from Earth. Also this would have to be huge amounts of supplies, enough to survive for approx 2 Earth years. So, if the project for some reason looses it's money source they're doomed. Second, it could end in a catastrophic disaster simply because those ppl would have to spend the rest of their lives with just themselves and some of them just may not endure this mentally. Third, assuming this mission will not fail, sooner or later they will have to regulate their population somehow, which also can lead to conflicts and further problems. IMHO, I think we should wait for the ability to return home before launching such missions.