"Contracts [...] can change, often without notification"
Sorry, but no.
Legislation states very clearly that a contract is a binding agreement between two parties. Any change must be met with agreement by both parties. That's the most important thing I learned in my feeble amount of commercial law studies as an accountant.
If SLA contracts can change without agreement of one party, then SLAs are worth no more than EULAs and should be ignored as such.
I am eagerly waiting for the day someone will finally have the guts and determination to disembowel this travesty of commercial contract once and for all, preferably with a red-hot katana.
Once upon a time, a contract was eye-to-eye, verbal agreement sealed by handshake. Once it was shook on, it was inviolate and unalterable, come flood or earthquake or meteor.
Today, commerce is nothing but a shark-infested pit filled to the gills with liars and nancys who will go to any length to not own up to their responsibilities and respect the word that was given. It is high time that the law was properly imposed on all this nonsense.