1. It was implied in this thread that space colonies would give us a way to reduce the over-population on Earth. WRONG. First of all, we already have a cure for over-population: condoms & the pill. Unfortunately a lot of religious people think that it's God's will that we go forth and "multiply." They use their influence on idiotic policies like abstinence only sex ed (proven not to work) & get in the way of spreading the message to developing countries that contraceptives will help prevent excess population. But, I digress. We are not sending significant numbers of people off this rock in order to reduce the population. So that you can wrap your brains around this point, consider the space shuttle. It takes 7 people off the Earth and is only capable of a LOW earth orbit. They can't even get to geosynchronous orbit; let alone somewhere else. But, stop and consider the amount of fuel & resources that goes into a single launch.
"But DrPizza, in the future, once we have fusion power, we'll be able to split water into oxygen and hydrogen and use that to power launch vehicles." So what? If we had a fleet of 10,000 space shuttles hauling people back and forth just from the earth to the moon, they wouldn't keep up with the rate at which the population is currently growing. i.e. Earth's population would continue to grow - back to the solutions which already exist.
2. I agree that humans should eventually colonize elsewhere in space. We are decades (even a century) from the technologies necessary to do so in a meaningful manner: fusion, different propulsion system for rockets, space elevator, etc. Of course, 50 years after fusion is developed, people will say "it was developed specifically so we'd have fuel for NASA." Much like many of the claims that various improvements/inventions wouldn't have happened without NASA. (Scratch resistant lenses? Really, you don't think someone would have thought of developing scratch resistant lenses, particularly after the switch from glass to plastic?)
3. At present time, the only reason for humans in space is public relations. The international space station is little more than just a public relations tool. (Name one bit of meaningful research they've done except to assess the effects of a microgravity environment on humans who are wasting time floating around? Just about anything else could have been done without humans.) Anything that humans can do for research, robots can do. And cheaper. MUCH cheaper. And any observation that would be made using a tool... ANY observation made with a tool, be it binoculars, a microscope, etc., is made by a human. Just think about a typical electron microscope - you're actually looking at an image produced by a computer and displayed on a screen. You can sit 1 foot from the microscope or 1 million miles; it's the exact same image. You don't have to worry about bringing robots back. You don't have to worry about life support for robots. They work longer hours. They don't have psychological problems after a long journey, they don't have physical problems from prolonged "weightlessness," etc.
3. The primary use of water on the moon would be to produce hydrogen and oxygen to use as fuel in rockets. As someone pointed out above, the moon would make an excellent base to launch things from due to the Moon's low gravity. BIG question though for you: exactly what are you planning to launch?? Ohhhh, I get it, you're going to launch things from the Earth, land them on the moon, then re-launch them again. Brilliant! Not much water would be needed for human survival.
"But DrPizza, how long can you go without drinking water?" It would obviously have to be an air tight environment. In such an environment, like in the ISS, water is recycled over and over and over. Urine -> water -> urine -> water ->... Of course, some water would be needed to grow plants (hydroponically, I'd assume) - but that too would have virtually zero losses once established. And if that's all we needed water for - a couple of greenhouses - it could be transported with today's technologies.
4. You'd think I was on Malak's side thus far. Absolutely NOT! I support doubling NASA's budget. Hell, triple or quadruple it. Just put the money toward more meaningful research rather than the public relations types of endeavors. Why not determine the actual rate of global warming? (especially since the satellite has been built, then mothballed by the Bush administration. Thanks Cheney.) We hit the moon with a probe; we've hit various other space objects with probes. How about exploring the moons of Jupiter for signs of extraterestrial live? And, this has to be done with probes: we can sanitize probes much better than we can sanitize humans. Else we can be certain that eventually we'll find signs of life elsewhere - it'll be from us. The discovery of a life form on another planet would probably be the greatest discovery in human history.