After a lot of thinking, the FED issued its rules for debit card interchange. Essentially they've outlined the borders beteen which the outcome in the market is acceptable. And it's a smart solution for a tricky debate, because at some point it looked as if the FED didn't really knew what they were up to.
An interesting element is that 3 party networks are excluded from the regulation (which is legally inevitable). And that a sort of competition appears to be forced upon the issuer. In any case, the markets reaction in terms of increasing share price was quite clear. Although it might also have been the short-squeeze in US treasuries that did the trick.