I started a thread a few days back in philosophy 'Imagining the Future' which touches on the same issue.
Regardless of how much we might like the idea of humans exploring space, the facts don't look too positive. Space is an unforgivingly deadly place, it's huge and it's very, very expensive to go there. Only the huge political motivation of the Cold War got the US to put a few men on the moon and they haven't been back since. Space isn't going to ge any less dangerous, we're not easily going to see technology which can reduce light-year distances by any significant margins and if anything, human space exploration is only looking more expensive as time goes on, not less. And, we have to ask, what does it achieve? Seriously, there's very little science in space that can't be done by probes and robots.
As I said in my own thread, I think we've been seduced by science fiction into expecting human space exploration to be the obvious 'next step' but it isn't adding up.