Why would that happen? Vendor lockin is a real concern, but worrying that AWS will decide they don't like you is not rational.
No vendor wants to earn a reputation of being that hostile to its own customer base, and so unless you are doing something that is likely going to raise eyebrows you'll be fine.
My account had 100% reputation, no billing issues and nothing in my account details was unverifiable.
Then the support rep told me that the account was closed by the system, maybe by mistake, but there was no way to reopen an account so I’d have to signup again and then open a support ticket for that account (I think it was to migrate data, no longer remember).
Annoyed, I try to signup again, open a ticket and the response was:
> We have reviewed your account and have determined that Twilio's services cannot support your account at this time due to one or more of the following:
> 1. Violations of Acceptable Use Policy 2. Violations of Twilio SendGrid Email Policy 3. Accounts with unresolved billing issues 4. Inability to verify provided information
> Thank you for your interest in Twilio SendGrid, best of luck with your future endeavors.
This was from an account with 100% reputation. What I think happened is they were purging low spending accounts. So yes, a company can definitely stop liking you. Gladly I was able to move very quickly to SES.
Big companies also just make mistakes. They can accidentally ban you and not feel like fixing it.