But if I find an interesting story via a site like BoingBoing, I09, Neatorama, MentalFloss, Dark Roasted Blend,etc., and then link to the original story, shouldn't I say where I found the link? On the other hand, some stories appear on multiple sites, do I have to cite all the sites I saw it on? Or decipher all the vias and hat tips they use to find out who posted it first?

But this often becomes the basis of a sort of ad hominem attack. "You found that story linked on a website I detest, therefore the story is bullshit in my eyes."

Completely agree with your last paragraph. I have always read a lot, and sometimes when Mrs. P. challenges one of my frequent factoids, I can only shrug my shoulders and tell her I couldn't possibly remember the source of something I read decades ago.

Attribution can get lost in its own density and egos. I had a psyc class in college where the final exam was more about who developed ideas than what the ideas were. Me, I studied the ideas and didn't worry about memorizing all the authors of the studies. I thought the prof was more interested in the history of the topic and not the models. Good thing I took that class pass/fail.