I believe the times when this would actually be a good thing are VERY rare.    Like I said it shouldn't be a matter of just wanting to erase memories.   Those negative memories and learning to deal with them are important.    The rare cases would be in cases where it is debilitating, or a person without a doubt is going to commit suicide if it remains.   Things like that.

Yet like I said that is pretty rare.   I consider any other use of this tool to be a very dark thing.