Interestingly, i do think there is a need for it. A mark that is only 1 thing, sarcasm was this sentence.
I'm on the fence with the "need" and definitely not sold on a patented or trademarked solution. Imagine the court battles when untrained employees of companies unwittingly forward or use this symbol and then the company is financially liable for this? The open source community would probably declare that @) or some such combination represents the same thing.
Yet another issue is this, at least for me. Why on Earth would you use sarcasm in a forum where without a symbol denoting it you may get into legal trouble? I mean fuck. If I wouldn't say "fuck," why would I say "fuck @)"

Sarcasm with a disclaimer also seems a bit gimped to me

Food for lazy Saturday brains
