I discovered last night that Charles Rivers Editors, one of Vook's partners, now have a series of enhanced ebooks in the Kindle Store. It's called "The Sock Puppet School of Business". As you might guess, all the clips star sock-puppets, not people. If you're curious about how they did it, here are a few free titles:
I've seen a couple clips, and aside from the giggle factor they're actually pretty good. The clips get the point across quite nicely.
Now that I've had time to think about it, I believe that niche technical markets like this are a good fit for enhanced ebooks. Like most Vook content, these ebooks started as regular books which then had clips added. the clips aren't integral to the text (but they are complementary). The videos reinforce points in the text.
The clips can add value by reinforcing a few details without the rest of the content being neglected. That is something that doesn't work so well with fiction. That's why I think we might see enhanced ebooks flourish in technical content, not fiction.