I thought this was an interesting social media mistake -> http://redcrosschat.org/2011/02/16/twitter-faux-pas/
Someone in charge of Twitter at Red Cross posted something, technically inappropriate I suppose, on their Twitter page. Luckily they were able to handle it with humor and grace resulting in an increase in donations. It really goes to show you that if you actually know how social media works you can really handle almost anything.
In general it’s a lot more interesting and revealing to see how companies respond to missteps than it is to watch them perform seamlessly.