I've so far avoided activating Facebook account integration, as I didn't want to clutter my People hub contacts that were originally loaded from my Hotmail (Windows Live) account with those from Facebook.
If I'm understanding correctly, Settings > applications > people can be used to navigate to an "Include Facebook friends as contacts" section and that "Only add Facebook info to existing contacts" is a radio button choice. Not sure what other choices are available, however. Since I don't currently see this section, I'm assuming that it appears only after going to the accounts section there and choosing "add an account" for Facebook.
I'm curious what "Only add Facebook info to existing contacts" actually means. For instance, what if your existing contact info conflicts with that in Facebook for a person? I'd prefer not to add any Facebook info to existing contacts, but suspect that it's not an option.
It sounds as though there's no current process to eliminate feed information for Facebook contacts who weren't also Hotmail/Windows Live contacts.
If you later remove your Facebook account from your phone, does your People hub contact list and information for those contacts return to what they were prior to the account being added (assuming that you didn't add or change any of them in the interim)? In other words, does any Facebook account contact information get synched to your Hotmail/Windows Live contact info after it's been imported, but not get reversed after the Facebook account is removed?
I'm having a difficult time finding much detailed documentation on Facebook integration, but hopefully anyone who's familiar with and has been using it will have some insights -- thanks.
I think "Only add Facebook info to existing contacts" will scan your Windows Live or Google contacts and only import any Facebook information from them if they already exist in one of those two groups. If they don't then people who you don't already have as contacts won't be added to your phone contacts.
As far as I know the accounts go through a "soft merge" on the phone. That is your contacts aren't all modified to have the same information. The phone takes care of keeping track of your contacts and the display to you but doesn't actually combine all of their information.