What's the movement from Bear Sterns to Merrill Lynch imply? It's the only one linking two failed entities..
Merrill Lynch was not bought by BoA until September 2008 and the merger did not legally complete until December of the same year (followed by company-wide rebranding throughout 2009). So I think the flow on the graph shows those that were made redundant when Bear Stearns collapsed in March 2008 and then went on to employment with ML before the BoA merger, which happened nine months later.
EDIT: grammar.
(† Why yes, we do use YAML...)