More on PFO

The PFO story goes on.  There have been studies to determine if  a PFO increases risk of stroke (the clinical trials are negative to date), migraine headaches (again the clinical trials are negative) and decompression sickness (DCS).  In the case of DCS, there is not likely to be a large prospective clinical trial because the number of people at risk is small and clinical trials are expensive so the cost benefit relation is not favorable.
The observations on divers with DCS and a PFO suggest that large PFOs impart some risk, while small PFOs don't.  Regardless, there is no risk if there are no or very few bubbles.  For most sport divers following their computer for no-D diving, there is minimal risk of bubbles forming in the veins and the PFO won't make much difference.  If you are a technical diver doing deep  dives or mixed gas dives, a large PFO might produce some risk.  Closing a PFO has its own risk, with the complication rate stated to be around 2-5%, while  the risk of a DCS event is much lower  - about 0.02 - 0.05%.
Based on these numbers, I would not recommend getting a PFO closed to improve risk for DCS, and certainly would not consider a PFO as a prohibition for diving.  You can find more details about a PFO at:  http://www.scubamed.com/PFO_page.html