I love this rule, since I had recently (late-July) emailed them saying I found it annoying how customers from the front of coach were constantly using the F lavs on smaller aircraft (S80, 737). Literally, I was counting 10-15 instances of this. On a 2-3 hour flight, this really adds up. Here's the reply I got at the time:

From: Americanairlines Wecaare001
Sent: Monday, July 26, 2004 1:57 PM
To: doogles
Subject: R2004/07-28480-00513-001


Dear doogles:

I'm sorry you have been inconvenienced when customers from our main cabin find it necessary to use the lavatory in the premium cabin aboard your flights. However, our policy is not to deny anyone the use of a lavatory in any cabin, regardless of their seat assignment. At the same time, our flight attendants should monitor the situation to minimize the disruptions to those seated in the premium cabins. I have shared your comments about this particular issue with our Vice President of Flight Service. We want all our customers to enjoy a pleasant ride when traveling with us.

This is an "outgoing only" email address. If you 'reply' to this message by simply selecting the reply button, we will not receive your additional comments. Please assist us in providing you with a timely response to any feedback you have for us by always sending us your email messages via AA.com at http://www.aa.com/customerrelations.

Sincerely,

[snipped]
Customer Relations
American Airlines