I think for the most part, they take advantage of people when they are at their lowest.
I was suffering from post-natal depression and was so scared for my children and their future. So one day, in the depths of despair, I prayed to God and asked him to help me and show me why everything was in such a mess. Low and behold two witnesses came knocking and then took 27 years of my and my families life.
As some have said, they seem to have the truth and when you question it you are told to wait on Jehovah. When you have doubts you feel, or are made to feel like it's you that has a problem with your faith, that you're weak.
My husband started to have a bible study just to try and disprove what they were teaching. Unfortunately he had no prior bible knowledge and they soon reeled him in. He looks back and can't believe what he did, but he's recovering his self esteem and starting to enjoy life again.
We still have a faith but not in any man made organisation. We're gonna have a party the day we're d'fed. And your all invited.