Valid point by Brent Simmons:
When Twitter was recently hacked, I was among those who got an email saying I was affected. So I changed my password.
But here’s what I’ve noticed: changing my password does not cause any of the Twitter clients on my iPhone to ask me again for authentication. They just keep working normally.
In such cases, it’d be wise indeed that the service (Twitter in this case) automatically revokes all authorized apps.
(via ★)
Note: Perhaps now’s the time to check which apps you’ve authorized on Twitter?
UPDATE 2013.02.21: Apparently Facebook has such a system in place: when you change your password, all tokens expire immediately and Facebook will return error code 190 / sub_code 460 (Error validating access token: The session has been invalidated because the user has changed the password) to all apps accessing the platform. — Thanks, Jurriaan!