One area where e-reader vendors have free reign in their attempts at interactivity is when it comes to implementing new features for their platforms.
Kobo has been doing this in its effort to integrate face-book and gameification doohickeys, although I can't really test it because I don't use face-book and enjoy gameified UIs about as much as I would having my toenails chewed off by a badger.
Which isn't a bad thing, per se, for Kobo. For every person like me, who hates the direction they've gone into, there's going to be at least one other person who thinks it's exactly what they've been looking for, the most brilliant thing since Spice Girls.
Amazon has been going in this direction as well, albeit in much less intrusive and more usable way (at least for me, see what I said above about polarized opinions). Popular highlights, for example, is a clever use of network data, re-contextualized into the book for the curious.
More interesting to me are the Public Notes, which are live, networked, footnotes. Imagine being able to issue a correction to a book and have it appear as a footnote in all copies of the book, automatically.
They haven't seen much uptake but I think that's because they didn't go far enough.
I think that all books should have the Public Notes by its author enabled by default and I think that they should let authors use HTML in their public notes. They don't need much HTML support: bold, italic, links, and maybe images. Send a plaintext version to legacy devices and the fancy HTML notes to newer ones. Then give authors a nice web-based GUI for creating and updating their notes.
It'd be popular. But it'd have to be on by default, otherwise it won't work.
These suggestions and these tactics don't apply to just Kobo and Kindle. Reading software has a long history of experimentation, starting with some of the early hypertext systems and continuing into the Multimedia CD-ROM era and that's before you even get into the possibilities the internet offers.