mike2010 - 10:57 pm on Mar 7, 2013 (gmt 0)
something else I also thought of after submitting that...
Is that Robots.txt kind of works differently than rel="nofollow" i would think.
PR might still be able to leak onto the external link if it's just Robots.txt'd.
rel="nofollow" specifically tells google "i don't want PR leaking onto this external link".