There is harm, yes. Regularly hosting AMAs will turn this website into a social platform like reddit. Regular discussion will die down as personalities take over. It's the quick road to decline. The internet isn't what it used to be, public forums need to be guarded from the influx of low-quality commenters that consider everything a social platform first and throw regular, on-topic discussion out of the window. In time, low-quality and high-quality commenters form two groups and when they interact, the high-quality commenters leave.