This is by no means a genealogy specific item, but as someone who works in information systems and security I am amazed at the breadth of permissions some convenience apps ask for online.
DO: Weigh the benefit you receive for the app in question. While it is nice to have an automatic connection from the Flickr to the Facebook, is it really worth access to ALL of my profile and my friends’ information? Or access to my chat?
DON’T: Deny all apps – some are quite useful. Common sense rules the day here.