I think a more compelling rationale is to be found in the types of skills that programming develops and simply in the ubiquity of programmable devices. As has been expressed elsewhere, learning to be a good programmer seems to entail making certain problem-solving skills become intuitive. (As one fellow blogger has put it, learning to "algorithmate".) And in today's world where the average iPhone packs computing power that would have classed it as a mainframe not so many years ago, the potential for innovation through programming is practically beyond comprehension. I also suspect-- though I concede that I am also guilty of fluffy argument here and would be hard pushed to substantiate this view-- that the mindset that is made intuitive through learning to program gives people a more intuitive grasp of other concepts crucial to understanding our universe, be it genetics or the syntax of language. But in any case, the computer is now so engrained into our day-to-day devices that I would argue that "understanding our universe" really entails understanding how the microchip and computer work just as much as it does understanding the atom, the laws of thermodynamics etc.
Or put another way, there's really no reason nowadays to view programming as a uniquely specialist, "nerdy" subject.
However, I have some implementational concerns. I worry, if programming was brought earlier on to the curriculum, about how severely it would be dumbed down; educators need to understand that "programming" doesn't mean drawing inane patterns with "turtle graphics" or similar glorified spirograph imitations. I also have mild concerns-- though from a UK perspective, yes, they are mild-- that having a stronger computing component to the curriculum could widen existing digital divides if, for example, basic computer literacy was sidelined. (However, I do disagree with an apparent over-obsession with "teaching" skills such as browsing the Internet or word processing to those children for who such skills are as intuitive as operating their iPod.)
I look forward to seeing what success this and other similar petitions in other countries may have. And if you are based in the UK, I urge you to sign this petition and encourage your friends and colleagues to do likewise.