I am also interested in a response to Rob's question.
I found the following example that shows a geographic path, but it is only one level deep (and therefore not much of a tree): Using the Path Shelf for From - To Pattern Analysis (http://www.tableausoftware.com/community/support/kb/using-path-shelf-pattern-analysis).
Is there a lovely example from Tableau that shows a website path analysis? My particular need is to visualize user paths through interactive phone calls from a massive database of xml records, a very similar problem to website path analysis.
The From-To Example above shows spreadsheet input. I assume it is also possible to input the data in an xml or cvs structured file?