Reason 1
Facebook recently pushed an update of their application, which requires a lot of additional permissions.
I tried to upgrade facebook application on my mobile, and got worried to see the permissions they are asking to run this application.
Take a look at this picture. I took 4 screenshots and combined together to get a single image.
Have a closer look at the permissions which is marked in red.
Your messages
Read your text messages (SMS or MMS)
Your personal information
Add or modify calendar events and send emails to guests without owner’s knowledge, read calendar events plus confidential information, read your own contact card.
Phone calls
Directly call phone numbers, read phone status and identity
Your social information
Modify your contacts, read call log, read your contacts, write call log
Storage
Modify or delete the contents of your SD card
Your accounts
Add or remove accounts, create accounts and set passwords
Your applications information
Re-order running apps, run at startup
Your accounts
Find accounts on the device
Reason 2
I am tired of being in Facebook.
I have been member of Facebook since 2003 and have been not active for past several years.
I am not giving up my Facebook account, just getting rid of mobile application.