http://spywareitdaiuyfo2sqb5vsg7mek5cjabdr73luhnda57t2hyuzg7yyd.onion/articles/firefox.html
"The types of information we collect includes your browser type, device type, device id, time zone, language, and other information related to the manner in which you access the Pocket Technologies. " So anytime you view a file in "your" Pocket, they know everything about the device you used to do it.