(Originally written at Wednesday, November 07, 2007)
Slightly related my last post. It relates to an interesting issue of whether we should share the bookshelf in the first place.
Why is it an issue? Well, privacy. Suppose someone is malicious and try to figure you out. The best way is to try to gather all information about you and work against you.
Another concern of mine is rather interesting and absolutely speculative, what if information I read will affect my thought and what if people could reconstruct it just from the information I read? That will open up a lot of interesting application. e.g. We might be able to predict what a person will do better.
Just like in other time series problem such as speech recognition and quantitative analysis. Human life could simply be defined by a series of time events. Some (forget the quote) believes that one human life could be stored in hard-disk and some starts to collect human life and see whether it could be model.
Information of what you read could tell a lot of who you are. Do you read Arthur C. Clarke? Do you read Jane Austen? Do you read Stephen King? Do you read Lora Roberts? From that information, one could build a machine learner to reverse map to who you are and how you make decision. We might just call this a kind of personality modeling.
It seems to me these are entirely possible from the standpoint of what we know. Yet, I still decide to share my bookshelf? Why?
Well, this was crystal-clear moment for me (and perhaps for you as well) which helps me to make a decision: Very simple, *I* am statistically in-significant.
If you happen to come to this web page, the only reason you come is because you are connected to me. How likely will that happened?
I know about 150 persons in my life. The world has about 6 billion. So that simply means the chance of me being discovered is around 1.5 x 10^-8. It is already pretty low.
Now, when other people know me and recommend me to someone else. Then this probability will be boosted up because 1) my PageRank will increase, 2) people follow my link deep enough will eventually discovered my bookshelves.
Yet, if I try to stay low-profile, (say not try to do SEO, not recommend any friends to go to my page) then it is reasonable to expect the factor mentioned is smaller than 1.
Further, 1.5 x 10^-8 is an upper bound as an estimate because
1, Not all my friends are interested in me (discounting factor : 0.6, a conservative one, the actual number is probably higher but I just don't want to face it. ;) )
2, My friends who are interested in me might not follow my links (discounting factor: 0.01)
So we are talking about an event with probability as low as 10^-9 or 10^-10 here. That seems to me close to cheap cryptographic algorithm.
But notice here, my security is not come from hiding or cryptography. My security merely come from my statistical insignificance. In English, I am very open but no one cares. And I am still a happy treebear. ;)
That's why you see my bookshelf. Long story for a simple decision. If you happen to read this, I hope you enjoy it.