Every day the average American "signs" several EULAs from different companies. Most software requires signatures, usually in the form of an "accept" button, even after that software has been purchased, without protections for the consumer. Most consumers are not even aware of what they are signing. (More than 50% of users spend less than 8 seconds "reading" an EULA)*.
While most companies have rights within that agreement to change the agreement at any time, the consumer is without any leverage of their own. Often the only recourse for no longer agreeing is to discontinue use. The company loses nothing, we lose the product without any kind of recourse available to us.
EULAs should be understandable by users, and shouldn't be changed with such frequency.
*Trained to Accept? -Rainer Böhme