With a living person you're always burdened with this idea of fair representation, treading this fine line between honoring the person, and yet you really look at the word "honor," it implies that you then have to address struggle and hardship and failure, and all these things that it means to be human, that you show the fullness of their life. If the person's living, they are able to interject.
If the subject is no longer living, the immediate question is do you have enough first-person material to really get that story across. You'd like to avoid it just being other people's memories and interpretations.
The visual quality of the cameras now is such that you can shoot with available light, and if people are willing to mount a microphone on the camera and maybe even on the subject, then you're good to go.
I knew as a young boy that addiction and alcoholism afflict people - good, loving people - in profound ways, and that some people - usually from those rare "normal" families that I longed for as a child and as an adult wonder if they even exist - didn't understand this and sort of looked down their noses at people suffering with addiction.
I felt like any individual's recovery was more important than the film I was making. And I actually felt that my presence was a form of witness that communicated to the people I was following that their lives mattered.
I felt that if people understood the struggle of recovery, then some of the stigma of addiction might be reduced because the audience would understand in a palpable way that addiction is a disease that tells the afflicted, despite years or even decades of heartbreaking evidence to the contrary, that using will make things better.