Not only that. I use the mobile interface rather than the app for two reasons: Sure, the app is badly done and buggy, but, most importantly, it gives Facebook permissions that they've shown time and again they shouldn't have. They've fucked up on more than one occasion, and I know casual users who balk at installing applications that request too many permissions.
That's definitely a contributing factor, in my opinion.
I haven't used iOS in a while, but a couple of years ago the web app was faster (!) and had more features (like liking on comments, not just on status updates) than the native app (presumably because the browser used a JIT for JavaScript and apps an interpreter). I would use the web app for everything except uploading pictures.
That's definitely a contributing factor, in my opinion.