You're forgetting one small point: you have to write two (or more) native apps once you go that route. Hence the reason Facebook's Android native app came out roughly 6 months after their iOS native app did.
That's true but wouldn't you (as of today) still be much more comfortable going that route with a non-trivial project? Less time spent on the cutting edge battling the idiosyncrasies of the platform and more time building your app.
It depends on the resources available. If I were a CEO and the company was flush with cash, I'd just brute force it by hiring native developers across all platforms or farm it out to specialized native dev shops. If was a CEO of a smaller company tight on cash with a bunch of web developers, however, I'd go the HTML5 or hybrid route because it'd be the best utilization of my company's time and resources. This isn't a black and white issue.
Definitely agree. I'm not sure why many people think its just so cut and dry. The tradeoffs between html5 vs native are pretty much known at this point. Take those and rationalize along with the resources you have available, the cost, and time you can afford. Just ship something.
you also need to write two (or more) web apps too. Each OS has dramatically different user interface paradigms. Sure, you can run an iOS looking app on Android or Windows Phone, but it's going to be awkward and out of place.
