I hope this gets used for good, not evil. Lots of sites (you know, those sites, they crop on on HN from time to time) flash up "give me your email address so I can send you spam" boxes before I can read the blog post. Or when it thinks I've gone somewhere else when in fact I just opened it in a new tab. Or if a momentarily switched away. I mostly close blogs that aggressively try to sell me things, but sometimes I want to read the content.

Conversations about what's an app and what's a document aside, I'd much rather documents didn't know anything about how they were being displayed.