So far, this incident appears to be more embarrassing than damaging. Judging by what can be seen in this video, the lost files consist mostly of mildly interesting administrative info, including leave and earnings statements [i.e., pay slips], Marine Security Guard Detachment mess fund records, and account ledgers. There was also one nugget of possibly sensitive information regarding payments to a local activist group. The only classified item was a contact report involving a Marine Security Guard and a local woman.
It's low-level stuff but still potentially exploitable by a hostile intelligence service, which makes this a serious compromise.
The records were lost when the Consulate sold old filing cabinets at a local auction in 2005. The purchaser of the cabinets evidently kept the files until sometime after September 2008 when, out of anger over a (mistaken) news report that a car used in an attack on Israeli soldiers had also been sold at auction by the U.S. Consulate, she took them to Fox News in Jerusalem. Fox News viewed the files before they were returned to the Consulate.
This is by no means the first time sensitive U.S. government materials have been lost when furniture and other surplus items were disposed of. I know of far worse cases, such as these, which occurred so long ago that it's no longer a problem to mention them:
-- In 1986, if I recall the date correctly, WTTG Metromedia News in Washington DC reported that Top Secret documents from the State Department were found at Lorton Reformatory - a now defunct Federal facility for prisoners from the District of Colombia - inside safes that the prisoners were refurbishing under a contract with the General Services Administration.
-- In 1992 (?) the General Accounting Office reported that the Department of Justice had disposed of computers whose hard drives still contained files of the U.S. Marshal Services's witness relocation program for the northeastern United States.
-- One day in 1988 I was having dinner with the U.S. Consul-General in Ciudad Juarez, Mexico, when the Consulate duty officer called him to report that a very responsible Mexican citizen was asking how he should return a dozen or so Light Anti-Tank Weapons that he had discovered inside 'empty' shipping containers he had purchased at Fort Bliss, Texas, earlier that day and had unwittingly brought back with him to Mexico.
Nothing nearly so serious was lost in Jerusalem, nevertheless, any sensitive information that goes out of U.S. government control in an overseas environment is potentially damaging. File it away under Lessons Learned, only, next time remember to remove that file before you sell the cabinet.