Why So Hard On The PSP Then?

So Sony are releasing Open Platform for the PS3 which allows "any desired third-party system software to be installed on it."

Unless I'm overlooking something surely this poses Sony exactly the same security risks as homebrew on the PSP? Worse in fact as Sony are opening the door and inviting everyone in to the party, rather than make us climb up the drainpipe of HENC and in through the bathroom window of Devhook.

So, Sony, what gives?