Many of these contracts contain a clause that the company can change the contract in the future without restriction and without necessarily notifying you of the changes, and you agree in advance to the changes, without knowing what they might be.

Apple has a version of this: "Apple reserves the right at any time to modify this Agreement and to impose new or additional terms or conditions on your use of the Service. Such modifications and additional terms and conditions will be effective immediately and incorporated into this Agreement. Your continued use of the Service will be deemed acceptance thereof."

Note that no notification is necessary of the changes to obtain your consent.

If these sorts of contract clauses are really legally binding there is a very serious problem with the legal system.

A fundamental limitation on contracts is you must gain something for any contract or contract update to be binding. So EULA's are only enforceable if you don't already have the right to use the software / service. In other words, Sony could not prevent people from using other OS's on Plantations that where not updated, but a patch could constitute value that allows them to get a new contract with you. As to a service like Facebook things get a little more tricky (and I don't know how that works out).