The problem Brown was trying to solve was an age-old one. He wanted to create a computer that would pass the Turing test, computer scientist Alan Turing's famous challenge to have a computer give answers to questiosn that are indistinguishable from a human being's answers. So far, no computer has ever passed the test, though some attempts have led to funny results.
So Brown fed Watson the contents of a site called Urban Dictionary, thinking that would be a good way to teach it to understand idioms and slang like " OMG." He didn't realize that Urban Dictionary is filled with profanity and sexual innuendo.
Oops!
Or as Watson would say, "!@#$."

An IBM Scientist Taught His Supercomputer To Swear Like A Sailor - Yahoo! Finance (http://finance.yahoo.com/news/ibm-scientist-taught-supercomputer-swear-192235345.html)