Are hashtags the 'sarcasm font' we've all been waiting for?

I've just finished reading an interesting article on the New York Times website, discussing the newly associated value Twitter has placed on the # symbol, known as a hashtag.

For those new to Twitter, or simply trying to understand the significance of the hash symbol in recent times; 
hashtags are a community-driven convention for adding additional context and metadata to your tweets. Originally created to group tweets together and make them more easily searchable, the # symbol is quickly becoming as colloquial a noun as 'tweet' and 'google'.

So while I was amused by the NYT author trying to define hashtags as "Twitter's secret handshake", and intrigued by more recent attempts to legitimise the hashtagged 'Promoted Tweets' by attaching serious social currency in the form of exclusive offers - but what really interests me about this whole discussion is something far bigger than Twitter or the entire social web.

The problem with typing your feelings
As long as the internet has enabled text based communication, users have quietly discussed the need for a way to express tone or context. Whether it's a sarcastic text message or a joking email, at some stage we've all secretly wished there was a globally recognised colour or font that would indicate our intentions to the recipient.

Could placing a # symbol before calling someone a dickhead get us out of legal trouble some day in the near future? 
Could those four combined lines one day become shorthand for all our emotions?

Hey, anything has to be better than these ;) and :(