I recall a definition of mental illness that requires it to have a negative impact on the person.
A mutation may be adaptive or maladaptive. It depends on the creature as a whole - and also the current environment.
That environment is analogous to the market part of "product+market" for a startup: the identical technology/product can be a winner or a loser, depending on extra-product factors.
I see that your reply to davidw was about actor/object; but I was replying to crayz, who was talking about "borrowing some DNA"/"being infected" ie. whether the effect was good or bad. hmmm... at least that's how I read him, anyway; but maybe he was also focusing on actor/object... regardless, I still say I have a valid point! :-) Good day, sir!