These weeks, I've worked on Evernote OAuth authentication of my iPhone app. Since the username/password authentication is going to be deprecated on the 1st November.
After move to OAuth, I can easily noticed that login page took very long time to load every time I launched the app.
So, I tested Evernote login page with a profiler (on computer) and this is what I discovered.

Loading javascript jQuery take 4 seconds and overall load time is almost 7 seconds. I had this test on coffee shop wifi, thus, I believed that it will be worse if the mobile apps are on unreliable network such as edge or 3G.
I think this is serious problem for third-party apps. Imagine that users launch an iPhone app for the first time, you require them to login, but they have to wait for login page (10+ seconds) before they can type anything.
PS. For comparison this's Facebook authentication page.












