I probably won't be using any EPUB3-capable devices/apps that don't offer the user the ability to turn off scripting support. Not because I worry much about privacy or data collection, but because I figure if they're not smart enough to severely limit what scripting in epubs can actually accomplish on their devices (or in their apps), it's only a matter of time before some script kiddie blows up my reader/tablet with a hostile ebook.
(well for those reasons, AND the fact that I find most retail EPUB3 are
pointlessly EPUB3. They'd've looked no different as EPUB2 books. I've
purchased some EPUB3s ... but they all got EPUB2-itized before before they found their way onto a reading device!
)