IMHO is that the iOS API is good, while the HTML5 API to do a lot of advanced stuff is still limited.
Can you give a few examples? HTML5, CSS and JavaScript support many features on mobile devices these days: geolocation, access to camera/microphone, orientation detection...
In short to develop a native application does NOT take more time than developing one in HTML5, at least for iOS devices.
But then if you want to support Android, you need another native app. And then another one again if you want to support, say, the new Windows phones. In contrast, a web app that is mobile friendly can be reasonably portable across platforms with a single codebase.
Moreover, even if you can develop your app within the same time frame, you still have the App Store approvals process to pass, and you have Apple cutting significantly into your revenues if you're charging.
Obviously these arguments probably don't apply to Facebook, but you said you were talking about a small startup, where everything above is definitely relevant.
That's what I saw observing the guys at Kiurma in the latest three years:
1) Most stuff is developed for Android and iOS, and all the rest is served via a CSS that is made mobile-friendly. So developing a native app for iOS + Android you cover 95% of the important target in the best way, and all the rest can stil access your services. So actually, for now, it's just two platforms and not N at least.
2) If you do the iOS application first, instead of trying to make the Android/iOS in parallel, then the Android app takes like 30% of the time of the first at max. You end just copying the iOS app just "translating it" into Java+Android SDK, so the time, in my experience is not 100% + 100%.
3) Anyway once you want to create a native look & feel in different devices, and want to make sure that the javascript, interaction, ..., all look the same across devices, even HTML5 is not exactly cut & paste.
4) It's true that apple takes 30%, but the possibilities of customers just hitting "purchase" button with a 0.99$ price tag or alike are a lot bigger compared to creating your way of making them paying. So IMHO the 30% cut often is justified by the advantages in the "processing" of the payment and in a raise in percentage of people motivated to buy because it's simply easier for them.
5) It's true that you can do stuff like playing videos, capturing images, or audio, or location. But trust me, if you try to do Instagram using this API the result is NOT the same. Doing stuff in HTML5 is often too slow, or you have too little control about how stuff is presented (see HTML5 playing of videos on iOS), or you can't use gestures well enough, or stuff are not working ok on Android or vice versa. Tons of problems.
6) A big pro of native is background. The iOS / Android location service that can awake your app when there is a significant change of position is extremely useful in a lot of social-alike apps.
So even with the small startup IMHO the quality you end with, responsiveness, and often also easy of development, more than justify to go native for everything but the most "just show some content" of the apps.
But after all, even Facebook should classify as a "most show a feed of stuff" app, that is one of the naturally prone to work in a decent way with HTML5, but still...
Can you give a few examples? HTML5, CSS and JavaScript support many features on mobile devices these days: geolocation, access to camera/microphone, orientation detection...
In short to develop a native application does NOT take more time than developing one in HTML5, at least for iOS devices.
But then if you want to support Android, you need another native app. And then another one again if you want to support, say, the new Windows phones. In contrast, a web app that is mobile friendly can be reasonably portable across platforms with a single codebase.
Moreover, even if you can develop your app within the same time frame, you still have the App Store approvals process to pass, and you have Apple cutting significantly into your revenues if you're charging.
Obviously these arguments probably don't apply to Facebook, but you said you were talking about a small startup, where everything above is definitely relevant.