Man To Mars: Why?
This guy makes a good point: Why should we spend so much money sending people to the moon and Mars? Nearly all the knowledge gained is of little practical use and could be duplicated using robots.
I'll have to admit being one of those who thinks heading to the stars is our destiny. On the more practical level, though, If the Cylons or The Borg ever find out where we are we'll likely need to get the heck out of here fast. Knowledge of manned space flight would certainly helpful in such an event.
Speaking of colonizing Mars, if you want to read a good book about it, try James Oberg's Mission To Mars. It's an oldie. I read it back when it was first published in '83. He's a NASA guy and tells how such a mission would likely take place. A fun and easy read as I remember it.
I wish I still had that book. It would be interesting to compare how he saw it to what we know today.