I assume "verified" means that Ashley Madison's server sent a verification email to that address, and the user at that address clicked on the verification link included in that email.

Certainly, someone might enter in barack.obama@whitehouse.gov for fun. Presumably, emails to that address (and the official public email address, president@whitehouse.gov) get routed somewhere. But who is checking the emails sent to the president's public address? That likely requires a team of people, one of whom might have clicked on the link.

Verification links gets clicked by mail scanning software (for malware, I suppose) all the time - if the GET isn't followed by a POST - the account is flagged valid.

As another data point, one of my gmail addresses is in the dump (Cf. https://xkcd.com/1279/ ) and listed as verified, despite me never clicking any verification link. Then again, I did contact support asking for them to remove my email address from the account (their response was to ask for money) and perhaps that did something.