Who pays for the cost of launch and the cost of controlling them?
Manned exploration is still the best way to go for the long term.
I fully agree that we have to have people in the loop. I also like the idea of lots of relatively cheap mini-probes instead of the mega probes that were sent out in the "golden age" of Voyager and the like. That was always my hope for the space station. That the astronauts would be doing final assembly and configs, or building up from on hand parts, small, simple, sensors to be deployed for further study. Put a good tether system up (above, relative to the space station) and I believe you could even launch these things cheaply beyond earth orbit. That only works with folks on orbit.
Of course my real hope is that someone will pull off a surprise and mount a private, money making, venture, such as snagging a platinum asteroid. Enlightened self interest. Always the best motivator.
One of my fondest memories was a long talk over beers with a co-worker in the IT group at my company who had worked (in normal IT, not on the program) at Grumman's Long Island facility where they built the LEM during the Apollo program. The story about all of them, even the janitors, showing up in the middle of the night looking to do whatever they could to bring Apollo 13 home was awesome. When he retired he left me all of his souveniers from those days, including the signed posters from the engieering team (plus some astronauts signatures).
Hey, didn't I see that on ebay?
WOW! :-) That is so cool!