It is so funny reading the posts of the naysayers.
I wonder whether you've read through the history of industrial revolution, the space age and the new technologies that you are using right now which were deemed "impossible" before someone came up with the invention and a few more invested to develop it.
I say, Elon Musk has the track record of delivering on his promises. One impossible thing that he made possible and viable was landing a reusable rocket ship back into a barge.
Previously, naysayers, and scientists at that, said that landing space shuttle is difficult enough -- which is like threading a needle from the 10th floor with the wind blowing.