Earlier quoted context omitted.
"If the wrong sorts of sites (however defined), sites outside my control, are linking to my site, why am I penalized, and why should the burden be placed on me to go fix it?" Well, if a website was link spamming then it seems appropriate that the site should attempt to clean up the spam they made before they can rank well in Google again. Otherwise it's not fair to the other websites that have been trying to rank fai…
So in this scenario, my competitors can spam links for my website and put me into trouble. Google will notice that my website has some spammy links (which my competitor created), and then penalize me for it. Then I have to contact every website that links to me to ask them to remove links to my website... else their website would get penalized too. I get such emails every week. Rather than these fear mongering tactic…
But! You may have hit the nail on the head. if i had to guess i would say that storing exceptions means that suddenly the algorithm had to check part of the corpus for these exceptions. at the scale at which google operates this could probably lead to rather big size and speed implications.
But maybe i'm just fantasizing.