Yeah, I think that a EULA change should reasonably permit for some kind of refund. Maybe have some mechanism for deprecating the value of the service based on use – like, if you expect a typical online game to be online for 10 years and a user has used it for 5 and the service wants to change the EULA, mandate the option for a 50% refund in lieu of continued service under the new EULA or something.

That’d make games more expensive, but it’s a risk that companies could factor in when deciding on EULAs and the initial price.