In my Fortune 25 company, we have a department of people devoted to resolving issues of people who contact the CEO, President, or other members of senior staff. This method absolutely will light a fire under the IT staff to fix it. I don't know whether he reads every incoming letter or email, but I do know that each one is handled by the presidential escalation team, and tracked, and reported out regularly.
We also have a Chief Information Security Officer who will personally latch onto this like a bulldog and ensure that it's fixed. We had a breach a number of years ago and it's still used as a reminder that "That will NOT happen again."