Can A Software Detect Subtext In A Speech, Such As Sarcasm?

If you are someone like the fictitious Sheldon Cooper from the famous sitcom The Big Bang Theory who has trouble in detecting sarcasm in a conversation you are not alone. The Secret Service of the US, yes the guys in black suits, tinted sunglasses and earpieces are having the same trouble. As you might be aware, these guys often monitor online chatter to detect any potentially nefarious activity such as an attack on an airport. In the recent past, they have had to intercept people who jokingly posted something about blowing an airport on Twitter. So in order to differentiate the actual threat to a fake one, it has posted #-Link-Snipped-# for tech companies on its FedBizOpps website where it is asking for a social networking data aggregation service that will be able to find the subtext in an interaction among other things.

So my question to fellow member of CE can a computer be able to detect subtext such as sarcasm? If, yes how and if, no why? For your reference, we have given a few links where the news was discussed: #-Link-Snipped-#, #-Link-Snipped-#, #-Link-Snipped-# & #-Link-Snipped-#