I think about this and I wonder if they don't add it because no internal team wants to take the responsibility of adding that feature. Imagine, FB source code is >10 year old code base, could there be a delete cascading effect somewhere? You mention posts, comments, likes and photos, what about game activity? Or notes? I think that's what were called. What is all your past information? Who defines what "all" past information is? What about Farmville game activity?

I'm not defending Facebook machiavellian tactics but knowing that no code base is perfect and also that even FB is understaffed, I will give them the benefit of the doubt.