In the early wave of Facebook apps there was a lot of stuff built that users hated. In 2010, when my cofounder and I started doing user tests of some Facebook app ideas, it turned out that people were very averse to using new apps. If you use a regular app and it sucks, you remove it. But if you used a Facebook app and it does something bad, you look like an idiot in front of all your friends. It was a classic tragedy of the commons: the viral behaviors that made early apps successful rapidly depleted the goodwill of users. And people didn't blame the obscure companies doing the BS; they blamed Facebook.
The lesson we took from our user studies was to build something that was an external website, and only mention Facebook integration once we'd had a chance to get them more comfortable with us. And I'm sure the lesson Facebook took was "don't let other people ruin our brand".