kyle:
Manned space exploration is a waste of resources. Absolutely unnecessary in terms of efficiency and tangible results. We have the technology to build self sustaining space flights without humans leaving Earth (and already have, numerous times). If you want to terraform a planet/moon, you should first sent bots to construct an human friendly environment that would be completely self sustaining. This is very possible. The process would take a while (20-50 years, pending biological technologies), but it would ultimately be less resource and time intensive than manned missions.
If you wanted to be even more efficient, you would have a fully functional space station set up at a Langrage point (where there's no net gravitational force acting on the space station, so it remains at a fixed point in space without using fuel). The station would need act as a service and construction center. Ideally, they would send raw materials to said station where bots (and astronauts I guess) could service and assemble whatever would be needed. Also, setting up extremely large solar panels at the station would allow it to act as a fueling station, so that the fuel needed to haul from Earth would be minimal, extremely reducing costs for Earth based launches.
In summary, send out robots and let humans reap the benefits later on.
As for who should be in charge of such a giant undertaking, it should (ideally) be an international effort of governments (whoever can contribute should be allowed in on it, sort of thing). Governments have more of a reason to do these sorts of things, I feel. Imagine if there were only one or two fully function hub stations. If private business owned these, they would have all space worthy nations by the balls. They could charge ridiculous amounts of money to even dock at their station, take some solar energy and leave. Etc etc etc.
*sigh* while scrutinizing the science of it you forgot the why of it. It is about expaning mankind into the galaxy and beyond, not mankinds artificially manufactured things (insert george carlin bit about 'stuff' here).
Exclusively using robots to explore space for you is akin to having someone fuck your woman for you.