Sticky is a term that has been used for a long time online. It usually refers to a site that is so engaging and fun that it keeps or 'sticks' the people who go to it. These new numbers from Facebook are crazy. The fact that they have so many users is something that has been talked about for a long time, but to have 70% check it on a daily basis - that is nuts!
Now one of the ways that they have done this is by creating multiple entries to their service via mobile devices. But still - your users have to open that app, that browser, and in some manner come back to your service.