Still a rumor that the US government has an interest in making banks keep TARP money, but anecdotal evidence abounds. This post ads some background to it and is an interesting read, but this myth isn't busted yet.
The structure of the test appears to be designed to ensure that no bank can pass it and therefore no bank will be allowed to return TARP money. The Fed/Treasury/FDIC/White House may decide that it's in the best interests of the country to not only make the banks keep the money, but also to have these banks scrub their balance sheets by selling "toxic" assets to the new Treasury program. This would be done under the motive that once the banks shed these assets, they can then start lending.
Thankfully we have the US government saving these bankers from the pitchforks, so they can return the TARP money ASAP and get to banking again.