In order to rid out the thousand trolls and angry people who just post nasty comments or troll or spam people's profiles, implement a way to allow only friends to post comments on your profile or to allow only friends to post.

Things to consider:
1. I know you can block trolls but many just make a new account or have friends and white knights who do trolling for them.

2. Some people want an open profile but it's a risk due to trolls or spammers posting bullshit on their profile, thus they have to resort to private profiles.