Twitter -- allow people to edit their tweets and put a check on the levenshtein distance between the edit and the original tweet and make it remain in some value range so that spelling mistakes can be fixed but tweets can't be radically changed.
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This is the best suggestion I've heard for edits, although I think the need for edits in the face of typos is itself a bit overblown. It's a casual communication medium, typos happen.
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True. Good point about the whole tech "just because we can, doesn't mean we should" argument.