In some fields (eg, finance) one can conceive a computer based process that would do a better job than most investigative journalists. It can't deal with missing data, but it can discover inaccuracies, unusual events and suspicious patterns and in some limited fields this is enough.
For example, an AI based process might have been just as good at finding the problems at Enron as conventional journalists were (since it the problems there were mostly uncovered by forensic accounting on their public balance sheets):
But hard information was scarce. "It's almost as if you have to use forensic accountants when you're doing a company story because many companies are using very aggressive accounting techniques that are perfectly legal," Shepard says.
http://www.washingtonpost.com/wp-dyn/articles/A64769-2002Jan...
Reporting a day at the races or the markets is easy because we know which kinds of data are relevant and we have them available.