A friend of mine sent me a link, incidentally about an MIT study about the futility of folio hats in blocking the thought police. I use Chrome for Gmail, but being the folio-hat -wearing type, I do all my other browsing in a tightly locked down FF. I copy-pasted the link to FF, and noticed that there was flash of a Google URL before it went to the right URL.
After pasting the link to a note, I noticed it's a Google referral link, similar to the ones most (all?) links on Google search are — in case you weren't aware. So now Google knows who sent what link to whom. The only way around that is to select the entire link, and copy the text.
Now, I'm aware that by definition of me being on a Google platform they implicitly know our conversations. But the fact that they bother to make a referral link means there is even more datamining going on behind the scenes than what we already knew of."