“If you cannot acquire them, copy them” is again true when we talk about facebook and twitter. Facebook after copying the twitter like layout has today introduced the twitter’s @reply like feature.
Facebook on its blog, mentioned that its like tagging people. Its more like tagging people in images and they let you tag people in the status messages or updates. 
You can not only tag people, friends but also events and pages. When you tag someone he/she will get update on wall linking to your post. The tagged person is allowed to remove the tag, similar to how tagging work in images.
Stay Digified !!
Sachin Khosla
