My initial thoughts (without having a ton of time to really absorb this yet) is that Apple's closed operating system may have just become a liability. The open 'intent' model of Android is really at the core of making something like this possible. In turn though does this also allow Facebook to take over "too many" aspects of Android and cut into Google's revenue streams as well? All things I'm still pondering. As an…
I'd call the inability for Facebook to usurp control over Apple's vertically integrated platform to be a market advantage, not a liability, as long as too many users don't start clamoring for a facebook-iphone. [edit] Remember browser toolbars? Now that Facebook is doing this, I expect this is just the beginning.
If the user decides to install a homescreen, and he does not like it, He will simply uninstall the app.