YouTube update?

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http://androidforums.com – The latest YouTube update came a couple days ago, for some reason my phone has not updated yet. However I'm not sure I want to update, in the app description it says the app now "preloads" on Froyo and Gingerbread devices. I'm on Gingerbread, but I need to spare all the memory I can get. The 'Galaxy S' can only handle so much. Can someone tell me what they mean by "preloading"? I do not want YouTube running 24/7. (General)