This afternoon a colleague and I were discussing text analysis and how there isn't a good way to do it in Tableau. We have seen demos for tools like Oracle Endeca that are all about analyzing unstructured text. An example that was often given was using it against doctors notes. The other is for occurrences of keywords.
I was able to use a "Split Fields to Rows" transform in Pentaho to make a row for each word and generate the viz below. I excluded numbers, and some common words like 'Tableau'. I also used a Stop Word List to exclude common words.