A lot of those people simply never get any external validation, have problems getting along with other people, and are unable to accept any kind of mentoring (while they desperately need it), in the end growing up believing in the greatness of their skills which in reality are not even mediocre. Since this seems to be the reason a large fraction of people does not finish their degrees, by this point as a recruiter I would just not hire a person without a degree.
For this reason, I would also ignore a lot of the testimonies that invariably will appear here of self-taught programmers proclaiming supposedly doing great, unless they have projects and code to back their claims up.
There certainly are exceptions, but do not start with the belief you will be one. Getting the same kind of wide perspective you get from a college degree from self-studying is several times as hard. I have self-studied mathematics after finishing my CS degree for a few years now and that's my practical experience. If you don't have the possibility to attend university, make sure to get as many opportunities as possible of verifying and testing your skills in different areas and stay modest.
This post by Notch of Minecraft fame illustrates all that I have said very well:
As far as practical advice goes, as soon as you are able to at all write working programs of non-trivial complexity (say, a platform game) MIT OCW is the place to be:
Taking those four courses in this order will provide a great basis, but I would be surprised if someone would be able to complete those in less than two years when self studying (I solved most exercises from SICP, learned a lot, but took me more than a year). To get the equivalent of a university degree, you would still need to heavily study at least four more topics: networking & security, compilers, operating systems and databases. Those two books might be a reasonable shortcut to learn some of this:
Source: I started working full-time as a developer when I was 19 and did it ever since, did a four year CS degree as evening studies after work (already having significant programming experience when starting the degree) and spent a significant amount of time self-studying (I worked through almost all of SICP, read the "Dragon Book", wrote a compiler etc.). I would never be where I am today (wherever it is) without teachers and colleagues from the university, there would be just lots and lots of gaps in my knowledge I would never get aware of.
While the variability of self-taught is higher than those with a CS degree, there are plenty of self-taught (without CS degree) software engineers who rise to the top of hard core software engineering companies (e.g. Microsoft, Facebook, VMware etc.), besides high-profile college drop-outs like Bill Gates and Mark Zuckerberg.
I suspect that your recruiter position expose you to lower than average quality candidates, as most good engineers never needed a recruiter -- they are simply referred by their friends and colleagues.
I am not sure if Mark Zuckerberg can be described as self taught,especially if you consider his high school's CS curriculum.
I also see myself being in more management of programmers at sometime. It's pretty rare for me to trivialization a solution process. I've done it, but so has everyone. Making mistakes is the learning process.
When I'm ready, I plan to start studying these resources.