What percentage of one's facebook friends does the average person really relate to on regular basis?

This isn't the kind of question that has a precise answer (yet). But It is food for thought. I think it would be interesting if a statistical study was performed on how many (percent) of the average person's facebook friends they actually talk to regularly. Personally I have about 125 friends so far and only about 25 I would message regularly. Many people I become friends with and then never look at their profile again. So whats your opinion? Do you have many friends that are there purely for the sake of upping your numbers of friends? I wonder if a term could be coined describing these facebook acquaintances you don't bother with.