Yes, i have.
There was an aunt of mine who has been diagnosed with late stage of lung cancer. Every hospitals that we went said that there is nothing that they can do execept alleviate the pain for her last moments.
At that time, the whole family decided to tell her that everything is going to be okay and opted for the pain relieving treatment.
At that time, i could see that the whole family is being dishonest, since they now every thing is not going to be okay and considering telling my aunt about it.. But i somehow understand because they do it out of compassion and not because they had harmful intention.