Facebook appears to have been helping themselves to users data, including call history and text messages. There's a big outcry, US federal investigation, etc. No doubt things will change for the better, sooner or later.
Usually the approach of "don't put anything private online" works, but if Facebook can look through your phone you lose that ability somewhat.
I thought about leaving Facebook, but it's just too useful to connect with friends and family, get event notifications, and share family photos. People not on Facebook tend to get forgotten.