Could Sovereign Debt Cause Run on Banks?

We ran this chart earlier, but it's worth running again, considering the Europe-wide carnage we saw today.
This is not just about sovereign debt. This is about a major freakout about the banking system.
The word from S&P is that Greek debt holders will take a major haircut on their holdings, and that means serious problems for banks. (See the full list of victims here)
Ths surging CDS of Portuguese and Spanish banks is a major red flag.