There are many things that they would not be able to add to a contract. Requiring you to commit an illegal act, for instance. Or beginning to charge for their s

There are many things that they would not be able to add to a contract. Requiring you to commit an illegal act, for instance. Or beginning to charge for their service, without giving you the ability to cancel your account. Instagram's change is in one of the grey areas that makes contract law interesting. (I am not a lawyer, this is not legal advice, yada yada)