When Twitter announced they were going to stop supporting browsers not on their list of supported browsers, I figured their attempts to block would be something more than just checking the value of the user-agent header.

They should just announce that users must use a particular user-agent header value and provide a list of approved values. If no one else compiles a list of acceptable user-agent header values for Twitter, I might have to do it.

Every user should just use the same user-agent header value. That would negate any utility of the user-agent header.