Molly Wood for the NYT, "Facebook Messenger Switch Controversy Is Part Misunderstanding, Part Mistrust":
But Facebook users believe they’re being forced to switch to a separate app to chat with their contacts. And they do not appear pleased. Messenger has a one-star rating from customers using it on the iPhone, with almost 6,422 reviews, from the last few days, as well as pages of negative reviews of the Android version. [...] The app does take some liberties compared with other messaging apps, although reading any app’s permissions is likely to give you pause. Messenger asks for access to your contacts, location, text messages, camera and microphone and more. And when you install it, its first request is to sync with the contacts on your phone. Good piece explaining the brouhaha over the change. I have Facebook Messenger on my phone, but declined every request for contact data, etc. I don't get many private messages on Facebook anyway. My girlfriend, on the other hand, heard about the permissions and immediately asked me to delete the app from her iPhone 4S. She wants no part of it, and I can't say that I blame her. See also: Phil Nickinson's story on this for Android Central.