[dpres]

With Chrome you should block all plugins, not just Java. You will still be able to watch a YouTube video by 'right' clicking the plugin's element and choosing 'Run This Plug-in'. Steps:

Settings | Under the Hood | Content Settings... | Plug-ins -> Block All

If you selectively disable plug-ins in Chrome you won't be shown the Plug-in element and won't be able to select 'Run This Plug-in'.

[_delirium]

You can also set Chrome so that plugin-requiring content is click-to-play, which I find a bit more convenient than block-all.