I know reading the friendly article (and especially PDFs linked from it) is not a certainty around these parts, but this one's pretty interesting. The article itself kind of entirely misses the point (whether the iDevice is a "computer" was pretty much completely irrelevant*), but the opinion itself taught me a lot. In particular, there are such things as "contributory infringement" and "inducement" in patent law. I did not know of such a thing until now.
All of the independent claims of the patent explicitly require a music source whose files have at least two types of metadata and a sorting feature (probably because "DAC-in-a-box" on its own is as old as the hills and not patentable). Assume for the purposes of discussion that the patent is valid (it's not**) and that an average mp3 file + iDevice (or most any mp3 player software) meets the metadata + sort criteria (doubly so if "file name" counts as one of the metadata).
Clearly, these companies are selling only the DAC-in-a-box, *not* including any kind of "computer", user interfaces, mp3 files, metadata or sort capabilities (although the end user can trivially add one and thus infringe the patent). Thus, most of the opinion - including a treasure trove of references to deciding cases - centers on whether the companies were liable for end-user infringements by encouraging and/or inducing them. The gist I got from the opinion is that merely knowing that a user *could* infringe is not enough - the manufacturer must either know of the patent (or believe beyond reasonable doubt that such a patent must exist), be shown to believe that it is valid, AND knowingly encourage an end user to commit actual infringement, or else be shown to have purposely avoided awareness of the existence of the patent ("willfull blindness"). Showing that you believed the patent invalid - in particular, obtaining and relying on an expert legal opinion of invalidity - is a strong defense against such "indirect infringement" claims. In other words, the burden is on the plaintiff to show indirect infringement, and the bar is pretty high.
* There is nothing about a "computer" in the independent claims (although one is briefly mentioned in a dependent claim) - only a list of features which could be performed by a computer (or iDevice). In fact, a footnote in the case notes mentions: "This Court declined to construct the term 'computer' and in this case the analysis need not turn on that definition." . For reasons I don't entirely understand, the check for direct infringement centered on the "interface" part of the claims, which the court constructed to mean a DAC (more or less).
** All of the claims were invalidated upon re-examination, several times (e.g. through several Bose objections to the reexamination results, including to the "Final Decision").