> We haven't kept someone in space long enough to reach mars
A quick google search says a trip to mars varies between 150-300 days. The longest human spaceflight exceeds that at 438 days aboard the Mir space station [1] from 1994-1995.
They're not comparable. Life in LEO gets protection from solar radiation. Life in space, on the surface of the Moon doesn't. Life on Mars gets some protection, but it still needs to be managed.
See e.g. http://www.mars-one.com/faq/health-and-ethics/how-much-radia...
But this is pretty basic for any Mars trip. I'm sure it's been considered.
I'm not one of the nay-sayers. Musk has a good record of getting things done, although sometimes maybe he pushes a little too hard.
I certainly don't think "That's s stupid waste of time and money."
And if Musk doesn't do it, someone else will.