(And even if you disable backups, Apple can still read most if not all of your messages, because the persons on the other side of the conversations have not disabled backups)
Having you messages deleted because you forgot your iCloud password is good security but a terrible default.
> Apple: "We have never heard of PRISM"[115] "We do not provide any government agency with direct access to our servers, and any government agency requesting customer data must get a court order."[115]
* https://en.wikipedia.org/wiki/PRISM_%28surveillance_program%...
Certainly American companies are subjects to warrants and NSLs, but Google (to give one example) had its dark fibre connections between data centres tapped by the NSA. Is that the "participation" that was referred to by the Snowden documents?
* https://arstechnica.com/tech-policy/2013/10/new-docs-show-ns...
* https://www.theguardian.com/technology/2013/oct/30/google-re...
* https://venturebeat.com/2013/11/25/level-3-google-yahoo/
* https://www.washingtonpost.com/world/national-security/nsa-i...
No, that's a separate thing. They do both. See the "you should use both" slide.
https://github.com/iamcryptoki/snowden-archive/blob/master/d...
As to the apple claims that they didn't participate in PRISM, I think they were just lying. Clapper lied to congress as well, so this isn't unheard of. They would likely have breached their government contract by telling the truth. That being said, them having never heard about the program name might be true because it might not have been known to them under that name, but that's just a detail.
It's been engrained in them since the 80s and with the growth of Google, it became fun to vilify Apple because of it.