Facebook is starting to track your mouse cursor. Here is what you should know.

Another site with a major usability issue. The black banner over the top is not considered when you click the scroll bar, so as a result there may be text neither at the bottom of one page, nor at the top of the next. Instead, it's hidden under that black bar, and only visible if you click the line-by-line scroll function.

Do you do this? Are you aware of the problem?

Sensationalist. A blog citing another blog citing a Wall Street Journal article citing a quote from a Facebook employee who probably was just giving examples of data that could be tracked. Decide for yourself.

"The social network may start collecting data on minute user interactions with its content, such as how long a user’s cursor hovers over a certain part of its website, or whether a user’s newsfeed is visible at a given moment on the screen of his or her mobile phone, Facebook analytics chief Ken Rudin said Tuesday during an interview."

Monitoring mouse movements might disclose some very personal information about a user, such as whether they suffer from a neurological impairment like Parkinson's disease.

Why does FB need this data? Isn't it enough that they track clicks, and they (should) know exactly where that link or button is placed in the user's current viewport?

I guess scrolling is important to know, in terms of how much time you spend looking at what's currently visible in the view port, and that the number of times you trigger the infinite scrolling is not granular enough to figure out which of the previous 10 items you spent the most time on (and didn't click through).