While the ptrace hole is clearly a higher priority class of security hole than a filesystem security hole, filesystem holes barely need the "victim's cooperation" to exploit anymore.
For example, at LCA2013, the swag bag contained a small USB key with a penguin logo. I'm amoung the probably majority of attendees who plugged that key into a laptop without disabling the default automounting. That could have easily been a mass exploit vector to access development machines for many Linux and free software developers and perhaps a LWN editor too. ;)
AFAIK it was not, nor was the PDF file on the drive that some attendees also opened.. But all that is needed to do such a mass exploit is an inexpensive hardware order and a bit of social engineering... and a "low priority" kernel security hole.