ProCD v. Zeidenberg
The 1996 US case that made shrinkwrap licences binding: terms you only see after paying still apply, provided you could have returned the product.
ProCD sold SelectPhone, a CD-ROM compiled from thousands of US phone directories, cheaply to consumers and expensively to businesses. Student Matthew Zeidenberg bought the consumer edition and put the data on the web. Phone numbers aren't copyrightable, so ProCD sued over the licence in the box instead.
Judge Frank Easterbrook of the Seventh Circuit sided with ProCD: "money now, terms later" is a legitimate way to form a contract, and installing rather than returning amounts to acceptance. Nor was the contract pre-empted by copyright law. A contract could therefore protect what the statute didn't, and the decision became the foundation for EULAs and clickwrap alike.