graeme_p - 5:46 pm on Jul 4, 2013 (gmt 0)
A few years ago my site was doing fine!
It it got hit by something in January last year. The timing looked like Panda.
I suspect the more PR you have, the more you can get away with is probably right. My internal pages mostly have a toolbar PR of 3, and most have 3 to 6 (it can be anywhere from zero to 20 though) in-content links, plus navigation and link to category. Seems reasonable to me.