Over the years, visitors to the Western Wall have developed a custom of placing notes in the cracks of Wall. The Chief Rabbi of the Western Wall, Rabbi Rabinowitz, says the tradition of leaving notes started nearly 300 years ago when a rabbi sent his students with a prayer in writing because he was unable to make the journey. Furthermore, the Talmud teaches that all prayers ascend to heaven through Jerusalem.
Today, with the 5 million people that visit the Western Wall each year, the cracks in the Wall are just bulging from all the notes. As the cracks become full, the caretakers of the Western Wall had to find a way to manage all the "paper work". So, twice a year, Rabbi Rabinowitz and his team "sweep" the Wall with wooden sticks. Their mission is to collect all the notes and then bury them on Jerusalem's Mount of Olives. The notes are treated with great respect and never read. In addition to the notes from the Wall, the hundreds of letters received by the post office (addressed to "God in Jerusalem") are buried at the same place.
As to why the notes are buried? Jewish law forbids the destruction of "holy text". Therefore, Jews have always discarded worn out prayer books, bibles, Torah scrolls, etc., by burying them in Jewish cemeteries. Since the notes left by visitors at the Western Wall are looked upon as "prayers", they are considered to be sacred and are treated with the utmost reverence.
