tl;dr
The issue in question was whether or not Dell's Terms and Conditions of Sale could legally force the company's customers to settle disputes through arbitration rather than in a court of law. This is the second time in recent history that the ninth circuit has found such arbitration clauses unenforceable due to the unconscionable burden they place upon the purchaser.
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The court based its ruling in Omstead v. Dell directly upon an earlier case, Oestreicher v. Alienware, in which Alienware (a Dell subsidiary) attempted to force Mr. Oestreicher into arbitration. In that decision, the court wrote that the Alienware contract was unconscionable because it was a "contract of adhesion." A contract of adhesion is a standardized contract, which, imposed and drafted by the party of superior bargaining strength, relegates to the subscribing party [the customer] only the opportunity to adhere to the contract or reject it.