[xcasperx]

I agree with what most people are saying on here, but I believe there's a bigger picture to it.

Let's say that your computer has been completely 'pwned', and that you are currently reading an article with an ad for Cow Porn, or whatever, on the right hand hand side of the site. The hacker can write some code to check what your eyes, and eyebrows, did when you looked at the ad. If it peaked your interest, the hacker can maliciously add more 'Cow Porn' ads to sites you visit - via swapping out the regular ones.

Now one day you get curious and click on it, and boom they take a screen shot and try to blackmail you.

This is obviously quite outlandish but think about purposefully planting posts, lets say on reddit, by switching out posts. They then look at your head movements, and, or, eye movements then boom, you're added to some list that you wouldn't have be added to if it weren't for your eye movements.