Where Does One Draw the Line?

I'm reading the delectable Miss Snark this morning (like ya do) and I came across this posting. In it the writer has this to say in reference to the whole Opal Mehta thingy (which I promised I wouldn't comment on again, but this is a different topic entirely, okay?):

I recently read an article by Katherine Paterson, author of a popular children’s novel Bridge to Terabithia. In the article, she talked about having unintentionally borrowed the word ‘Terabithia’, as well as a few character traits and fantasy elements, from the Chronicles of Narnia.

In Phillip Pullman’s The Northern Lights (The Golden Compass) he actually said he’d borrowed from many authors, crediting the wondering ideas of others for enriching his works.

I imagine it happens more often than we think: writers having great ideas, a great character, a terrific word… only to find out that they’ve pinched it, years down the track, while reading an old childhood favourite. But where is the line?

Legitimate question, I guess. Snark's reply is completely appropos, with this little nugget of wisdom as well:

"In this day and age it's not only morally wrong to steal it's STUPID. Eagle eyed librarians can summon up comparisons with the flick of a rhinestone crusted digit. Bloggers can sound the alarum far and wide".

Damn straight we can! Full disclosure demands that I inform you that there's not a rhinestone to be seen on my respective digits. I cannot vouch for the whole of my profession, however.

This all reminds me of the recent Harriet Ziefert scandal that everyone is so carefully not talking about anymore. I believe that Ziefert's excuse was near identical to Kaavya Viswanathan's at the time. Mainly, that she may have seen the book (for crying out loud, it had the same title) in the past but that any similarities were unconscious on her part.