I wouldn't sweat it. I think most people don't know about the AR-11 requirement. I think right after Sept. 11 the government used it (or attempted to use it) to deport some individuals. It is one of the few things that carry a penalty of deportation for failing to update your address. Anyway, as I said at the beginning, you shouldn't sweat it, in practice I believe it is never an issue.
http://www.uscis.gov/propub/ProPubVAP.jsp?dockey=790c96cac9f259897131086cb140e31c
The law in this respect is particularly merciless:
"(b) Any alien or any parent or legal guardian in the United States of any alien who fails to give written notice to the Attorney General, as required by section 265 of this title, shall be guilty of a misdemeanor and shall, upon conviction thereof, be fined not to exceed $200 or be imprisoned not more than thirty days, or both. Irrespective of whether an alien is convicted and punished as herein provided, any alien who fails to give written notice to the Attorney General, as required by section 265 ,
shall be taken into custody and removed in the manner provided by chapter 4 of this title, unless such alien establishes to the satisfaction of the Attorney General that such failure was reasonably excusable or was not willful. "
I think the devil is in the details, about the failure being reasonably excusable or not willful. Most people don't know about this requirement so they could show it was not a willful omission. A few years ago the government tried to insert text in most or all immigration forms reminding of this requirement to update the address, and to acknowledge understanding the requirement and its consequences. Fortunately, I think this plan died before being approved.
This document is particularly eye-opening on the issue (scroll down to the AR-11 sections):
http://www.aila.org/content/default.aspx?bc=7153
My 2 cents
(I am not a lawyer, I am just stating what I remember seeing in this forum and in the media).