OP here. Three things:

1. Most countries that have tried wealth taxes have either abandoned them or have had to constantly readjust them due to logistical difficulties and capital flight. They're elegant in theory, but very difficult practically.

2. The problem with ProPublica's coverage is that it was a tax policy argument masquerading as a news story. If they wanted to advocate for whatever policy position, that's fine! But to paint specific individuals as underpaying in taxes is deeply disingenuous. It poisons the civic well and gives casual readers the sense that something nefarious is happening.

3. Violating right-to-privacy laws to illustrate a policy proposal is bad! Really bad!