They do tricks and hacks for increasing retention rate the facebook Menu case.
When you click on the menu button they make the loading takes a long time because they have a high probability estimate that you will logout. They by doing that increase their chance to you receiving a message from one of your friends or continuing your browsing or leaving your account online and switching to another window. If big companies with billions on cash make tricks and hacks what will a small startup do? Growth hacking was a trending topic three years ago. I delved into it and I got some that work still today but I learned that Permission Marketing is better why they are not trying to do Permission Marketing. Spamming; disturbing and tricking people isn't a sustainable path of growth.
If you want to learn about permission marketing look at THIS
I even didn't finish this post that it happened one of my friends just throw me a message on Facebook.
