In addition to nationalization, he is also demanding their gold to be repatriated:

http://www.bloomberg.com/news/2011-08-18/chavez-emptying-bank-of-england-vault-as-venezuela-brings-back-gold-hoard.html

About 99 tons of Venezuelan gold is being held at the Bank of England. If the physical supply is indeed tight and the central banks have leased out their gold as some claim, then this action could expose the true gold situation. The central banks of europe and the US Fed refuse to discuss the role of gold in their monetary policies. Ron Paul has been asking for an audit of US gold reserves without success. It's somewhat ironic that the actions of Chavez could could expose the hidden activities of the western central banks.