I'm not so sure - don't confuse the general consensus on HN with the wider public. Average Joe won't think twice about clicking "install" on that dialog that tells him to install Flash in order to watch the movie he's been looking forward to.
I have no stats on this, only anecdotes, but most people I know are annoyed at having to install flash, or java, or any other plugins. They usually will, but they are still annoyed. That's the first step, IMO
Of course they are, but in my opinion it's more of the "oh, there's another iOS update already?" - kind of annoying. It interrupts whatever they were intending to do, but I rarely see any real objection attached to it. Then again, it's all just anecdotes.
