All you have to do is head to Settings -> General -> Restrictions and turn the YouTube app OFF. This will cause all video links to launch the YouTube web app, which I definitely prefer over the lackluster native app. Relevant search results show up faster in the web app and I find it much easier to share URLs by tapping in the URL bar instead of generating an e-mail in the native app and copying the URL from there.
Oh, and while you're still in Restrictions, you should probably also turn Ping off because it's, well, completely useless.
TAGS: iOS 5