Failure atlas
Privacy tools that did not hide what users thought
Hiding one field and leaking another.
What to keep
Some designs hide amounts and leave the graph. Some hide the graph and leave the fact of a transaction. Some depend on a trusted setup or on users who reuse behaviour.
A privacy paper should be read for the exact property it claims, then checked against how people actually used it.
What this is not
Not a complaint, not a price chart, and not a complete history. Primary sources outrank this summary.