We have pre-filled taxes in Denmark and they work fine. You have a month to look over the pre-filled forms and revise them if necessary. Although the tax system is also a lot less complex (taxes are high, but also simple). I know the IRS is doing something like that, just not giving it to you, which seems silly: I've gotten a letter before pointing out that I filled out a line incorrectly, which also told me what the IRS thought the correct value should be. I'm sure that was auto-detected by comparing something I entered with the W2 or 1099 information (I forget in which context it came up). So just pre-fill it for me, then, since you obviously already know what should go there!
[1] http://www.propublica.org/article/how-the-maker-of-turbotax-...