>The big thing is that you put quotes around it or otherwise acknowledge that you aren't claiming it as your own work. Which I think we all do!

Yup, I agree with this. In this forum, I have often seen people who got complimented on a quote susequently replying that they were quoting someone else.

Here, I think the acknowledgements are not done when the person feels it is obvious the quote is not theirs...eg, if I said "I cannot tell a lie" in the U.S. I would certainly not need to specify that George Washington was the one famous for having said this.