In addition to other bad things already mentioned, any government enforcement usually comes with "prosecutorial discretion" -- freedom to choose whom to prosecu

In addition to other bad things already mentioned, any government enforcement usually comes with "prosecutorial discretion" -- freedom to choose whom to prosecute and whom to ignore. Tracking all money spent would give a huge additional opportunity to many government agencies to harass those they find obnoxious. I have little doubt it would get misused very soon.