Content Leak: The band named their 3rd album "Steal This Album' which refers to how unfinished versions of the tracks got leaked before the album, originally titled 'Toxicity II', was leaked several months before it became commercially available.
Throw It In! - The beginning to "Chop Suey!" is three drumstick taps and the engineer's voice saying "We're rolling 'Suicide'", the track's working title.
In all fairness, they haven't permanently split up so much as taken a long hiatus, which ends (at the time of writing) this summer with their reunion tour. Fans can only hope this leads to new material, but there hasn't been mention of this from the band.
There's also a LOT of material that never got officially released by the band, mostly appearing on file-sharing networks and bootleg albums. As System of a Down took a lot of time between albums (three between the self-titled and Toxicity, three between Steal This Album! and Mezmerize/Hypnotize), it makes one wonder if they had other albums planned during those times.