There's more than a few password dumps out there from hacks. All you have to do is look and see that there's a few thousand words and phrases that make up something like 99% of the passwords used in those dumps. How many people memorized bible verses, Shakespeare, plays, music, stupid mnemonics, etc? It's not hard coming up with long, memorable passwords. If you use it regularly and don't take the lazy way of having your browser save them, they're easier to remember from repeated use.
@onep: thanks for linking that. I was thinking about the same thing!

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