The app has been singled out as an example of how easily people give data away!
The 'What are your most used words on Facebook' app might sound like fun, but it has been described as a 'privacy nightmare'. It is by far not the only app that accesses personal information on the site, usually with the full permission of its users, but it has been singled out as an example of how easily people give their data away

An app that shows your most-used words on Facebook might sound like fun, but the third-party software has been described as a ‘privacy nightmare’.
Some 17.8 million people have used Vonvon’s ‘What are your most used words on Facebook’ app in recent weeks.
But in doing so, they have given the company access to private details such as their age, friend list, education and hometown
Read more: http://www.dailymail.co.uk/sciencetech/article-3333324/Facebook-s-Used-Words-app-privacy-nightmare-Tool-used-highlight-easy-users-away-personal-details.html