I think the ability to opt out is something important in fandom. Because, exactly as you say, concrit can be as exhausting to give as it can be hard for some to receive. I spend hours during the week transcribing proofing marks before I go to talk to writers because the original transcripts are filled with 'WTF??!' 'I suspect drugs at this point' and 'Only a lunatic would suggest this'. They never need to know that my 'Could we restucture this so the shift from A to B to C is more organic?' began life as 'AAAARGH! I MUST KILL! KILL!!!'

I have to say that the few friends I have who like concrit and ask for it are often fun to talk with about their writing, as while I am all for the Death of the Author in theory, chatting with live ones can illuminate readings and meanings that would be harder to reach on your own.