Actually, thank goodness, the ruling did not reverse the 1984 Betamax ruling - The BBC seems to have mis-reported it somewhat in their summary.

the court said that that original standard [Betamax] still applied -- but that the non-infringing use shield wasn't enough to protect a company that actively induced or encouraged the use of its products for copyright infringement.

From ZDNet, and see also The Register. In other words, in fact in my words, and I am no lawyer - Apple can't be sued for making the ipod, but could be sued for trying to make money, more sales, by promoting or encouraging infringing use. Hence those file-sharing companies that advertised the possiblities of infringement now have to take responsibility for encouraging it directly. There will be ambiguities as to what defines "actively inducing or encouraging" but the Supreme Court likes to leave that to the lower court to decide. That's where it could get mucky.