Sony pulls two PSP games from PSN to prevent Vita hack
The hack in question allows users to run unsigned code on the Vita in "PSP mode," enabling homebrew programming using the system's PSP emulation. In other words, it's possible to run stuff on the Vita with an exploit, but nothing that uses the full processing power of the system.
We're optimistically hoping that Sony is looking into a patch for the exploit, so that it can resume selling those games. Making two games unavailable is a pretty terrible permanent solution.