It seems like something personal for the General, and I bet he is pissed it is in the news.
From the National Park Service website:
“Items are left at the Vietnam Veterans Memorial constantly by many, although not all, of the visitors. They are usually collected by NPS rangers at the site two times per day, once during the day shift and once during the night shift. In bad weather, artifacts are collected more frequently. The artifacts are tagged, given a unique identification number, and placed in museum storage bags. Note that Memorial Day (the last Monday in May) and Veterans’ Day (November 11th) tend to be the heaviest days of the year in terms of both visitorship and artifacts left. Independence Day (July 4th), Father’s Day (third Sunday in June), and days on which there is a significant event on the Mall are also fairly heavy. Then, the artifacts are stored on the Mall until a staff member brings them to the Museum and Resource Center (MRCE). Almost everything is saved for the collection. The only things that are not saved are active organic items (such as live plant matter) and U.S. National flags, unless the flags have been altered in some way. The unaltered flags are given by the rangers to Veteran’s Hospitals, Memorial visitors, or civic groups such as the Boy Scouts and Girl Scouts. Once at the MRC, the artifacts are identified, researched, and eventually cataloged. When items are cataloged, a detailed description is written of them, and a report is prepared on their condition. Cataloging is done for the security of the collections, and in order to have an easy reference on the collection for exhibits, conservation, and the like.”
http://www.nps.gov/mrc/vvmc/faqs.htm
I believe that all messages left at The Wall are collected, catalogued and preserved every day.