Martin Sandbu (FT) identifies four myths about wealth taxes:
Its too hard to do - well that hasn't stopped both Switzerland & Norway doing it (pretty well);
It won't actually raise much money - both countries above it raises substantial revenue;
It will scare the rich away - well it seldom does & then often they go to Switzerland (err, that has wealth taxes);
It will depress investment - no evidence backs up this claim.
So there we have it; wealth taxes are clearly possible!