The infrastructure required to support humans in deep space is daunting, but not impossible. Cost is a primary issue, but I see it as an investment. Nuclear submarines can support life as long as there is food on board. If you have the same tech, and a bit more room to work with...

The rovers on Mars are doing an amazing job, but in well over three years, Spirit has gone how far? About four miles? It can take operators days to plan and execute actions as simple as moving to the other side of a rock. I suspect teams of human geologists with more facilities would have collected a lot more information by now.

The one thing a human being is, is flexible. The probes and landers we've seen are painstakingly and brilliantly engineered to perform a small number of tasks. To do a new task, you would have to bring along a new device. Watch an on-site geologist work for a day or two, shoveling, climbing, snapping rock loose, examining things in a field lab, and trudging through sand, gravel, snow, puddles, and over rough terrain. A geologist can carry a twenty-pound rock, or sort grains of sand with a tweezers.

Once you have passed the initial hurdle of putting a base on Mars, the rest gets (relatively) easier and cheaper. Set up the transportation to the point where dozens to hundreds of humans can get back and forth, and you're doing the equivalent of sending thousands of rovers to Mars.

An intermediate solution would be teleoperated equipment run from Mars orbit in real time (would allow a lot of productivity while more infrastructure is being transported), but sooner or later, people are going to want to get dust on their feet.

I'm using Mars as an example here, but this applies across the board to the Moon, asteroids, and elsewhere. There may be areas where robots are going to be preferable for a very long time--the surface of Venus comes to mind--but at some point you're going to want people on the scene.

Now there may be super advances in technology over the next few hundred years--truly intelligent adaptable robots, or modifications to humans that allow them to live and work in space without a lot of support, or for that matter, Star Gates that would let you walk to Mars. But I'm talking here and now for the most part. There's no technology required for human space exploration that isn't pretty much in our hands already.