Moreover, that Hayek's predictions failed to materialize is a testament to the degree to which we've internalized many of his arguments in the book. I would argue that the same can be said for Marx. The extremes that both men were railing against no longer exist as credible threats to our society, despite what some will have you believe. In re-reading these texts, their arguments would almost seem quaint were it not for the recognition that the problems were, at the time, very real.
The flip side to all of this is that this particular book has lost much of its relevancy to the problems we are dealing with today, much in the same way that many of Marx's writings are of little use in addressing contemporary issues. That may not please the self-styled radicals at either end of the ideological spectrum, but for the rest of us it is very good news indeed.
I was never impressed with Road to Serfdom, but I suspect it is for this reason. From the perspective of 1942, when the world was terrifying and nearly all economies were commanded and controlled, it probably made a lot more sense. Getting on a high horse and waiving the book in the air in 2010 doesn't.
Meanwhile, Brad DeLong asks how much the market organization of economic life matters, which is what Hayek (and Marx) were really concerned about? Almost a factor of 10, as it turns out.