[iaskwhy]

I believe Facebook is the most amazing social interaction thing ever made so I kind have this need to correct some of the things you said, sorry!

Friends: If you reject someone from being your friend they are not informed about it but, if they are smart enough, they can check your profile page and see if they can add you again; you can also block that person and he won't be able to ask to be your friend again; I think this is almost perfect, the only problem I see here is the word "friend". You can accept someone and add that person to a list which will make that person unable to see anything if you want to while still being "friends". Oh, you can also just forget about accepting friendships you don't want to have, the person asking for it will know you still didn't accept him but that's about it.

Emails: You can disable all email notifications (or toggle most of them off leaving the most important on, it's really well done) going to "My Account", "Notifications" tab.

Tagging: You can make your default friends' settings restrict things like seeing photos. If you want some of them to see those photos you can add them to a list where you let them see photos.

Vender Lock-In: I'm not sure about this but didn't Open Social just solve this problem?