I think that we all devlop our style and working practices as we take more photographs. When I started out, it never occurred to me to spend time removing dust and scratches either. However, as I scanned more pictures, I became more particular about the results I was getting, and now I wouldn't dream of uploading pics with visible dust and scratches on them.
In the case of the pic referred to on this thread, I would have removed the hair (for it is pretty certainly a small hair that got onto the original when scanned) in the editing stage. However, it's not my shot, and in this case it's not so bad that it really spoils the pic.
I'd quite like to see pics rejected when they have significant dust/hairs and/or scratches on them though. Sometimes there are pics where there is a big dark hair in the middle of the sky - which detracts so much from the quality of it, but which would have been so simple for the photographer to remove.