I haven't forgotten that at all. However you seem to have forgotten that quite a bit of SpaceX's funding comes from NASA these days. They aren't doing what they are doing as a charity. There is no direct profit motive or compelling business case to be made for a Mars trip. It's pure research and expensive research at that. It's not at all inconceivable that the price tag for a Mars mission might be well over $1 Trillion. Even if you drop that by an order of magnitude or more it's still a ludicrous amount of money. You are NOT going to crowd source a project with a price tag that big. There either has to be a profit motive or there has to be one or more motivated nation states involved when you get to that sort of expense. We're not talking about a Kickstarter campaign here.
Some of the money is from NASA's commercial crew, etc, but that is a few launches a year. Have you actually looked at SpaceX's launch manifest? They are booked solid through 2017 or so, with a variety of customers. They have set a target to capture 50% of the launch market for Falcon 9 class vehicles and they are well on their way to doing so. What's more, the lower costs they are providing are bringing a lot of previously unprofitable business models out of the woodwork, which become viable as soon as launch costs head downwards. Google's whole Teledesic v2 initiative is enabled by this, and that's hundreds of satellites. Lower costs are changing things, and we can't make the old assumptions any more.
LEO is nowhere close to halfway to Mars, literally or figuratively. Thinking that just getting to LEO means you're mostly there is naive.
My initial statement was in terms of delta v. LEO from Kennedy Space Center takes ~10 km/s of delta v. Mars from LEO is ~ 5 km/s. So, indeed, you are about 2/3rds of the way to Mars capture once you have reached LEO, in terms of the propulsion required. There are other difficulties, but we know fairly well how to keep humans alive in space for long durations thanks to the ISS (on the scale of many months which will be required for a Mars transfer), and there's good reason to believe that transferring from space to Mars will be less difficult for the body than space to Earth.
With respect to the radiation risk, I will copy something I posted in another reply:
This is a solvable problem. The serious danger to life (as in, kill you before you get to Mars) comes from unpredictable solar activity, and you handle that by storing your fuel, water, and other significant mass behind you (pointed towards the sun). The remainder of the threat comes from galactic cosmic radiation, and this is a predictable, low-level dose. We don't understand the impact of these long term low dose rates very well though... the projected cancer risk depends on the veracity of the Linear No Threshold model, and we've got good reasons to believe that this isn't telling the whole story. It very well might be the case that low levels of background radiation don't have a detectable impact on cancer rates. The fact that Colorado experiences higher constant radiation due to uranium in the soil and lower atmospheric shielding means that the residents experience more radiation than the rest of the US, yet Colorado's average lifespan is longer.
So, GCR might have an impact, it might not. Even assuming that LNT is accurate, though, the risk is still potentially tolerable. Suppose it doubles your cancer risk - there's still a good chance that heart disease is still the dominant factor in your lifespan, not to mention the considerable risk of launch and reentry. We shouldn't make radiation more of an issue than is warranted - if you've got a 1% chance of dying on launch/reentry, it doesn't make sense to call off a mission because it gives you a .5% chance of dying in the next 20 years from cancer. You're inconsistently allowing one type of risk and disallowing another.
One suggestion I've seen is to send smokers, who then quit cold turkey. Besides the obvious social/physiological issues with this, the data shows that a person quitting smoking and substituting the galactic background radiation would come out ahead in terms of life expectancy - so this tells you what level of risk we're talking about. If a trip to Mars poses less cancer risk than another legal activity that people willfully engage in, that says to me that it is an acceptable level of risk for an informed person to choose to take.
The end result is, there are no deal breakers here, and while I agree that 12 years is aggressive perhaps to the point of folly, I think that the 2040s projections are weakminded and equate to never accomplishing anything, since we've got no demonstrable capability to keep our focus for that amount of time.