Publishers would, of course, have to make this available separately from all of the individual formats, and charge a little more. After all, they'd be technically selling three copies of the book, and that could potentially provide copies to three different people who would otherwise have bought their own. However, that certainly won't always be the case.
I think families might benefit from this the most. Most nuclear families I know share books, and are unlikely to purchase more than one copy of the same title. Still, they may prefer different formats. Some families have one avid paper-book reader, one person who loves listening to audiobooks during commutes or while exercising, and one who packs a Kindle while traveling. These families - the ones I know, at least - are unlikely to buy several versions of a new book, but might shell out a few extra bucks to get the options.
I don't know too much about the e-book situation at the moment, not being myself possessed of an e-reader, but here's my understanding of it: E-books are usually released months after the hardcover book, with Dan Brown having defied that practice with his newest book. Publishers are concerned because e-books are so much cheaper that they fear hardcover sales will drop if they release the e-books at the same time. Unfortunately, the availability of the paper books without the corresponding e-books means that pirated copies hit the Net with no competition, and the publishers (and authors) lose money anyway. The multimedia package could be a way to prevent this from happening - although, of course, it sort of assumes the simultaneous release of hardcovers and e-books.
1. After struggling a little with the specific ages of two characters in The Dogwatchers, I liked this fellow's pondering of characters' ages in literature. Includes a link to the blog project he's working on, which will contain a male and female literary character of every age from, apparently, conception to seventy. (Don't hold your breath, though - he's still in the toddler years now.)
2. A brief article analyzes trends among the 7,200 books left behind in UK hotel rooms over the past year.
3. Silly examples of how some classic books might have been titled differently were they published today.