Death, doom, destruction, etc.
Haha... Yote, you crack me up.
A reef tank, contains, by definition, stuff from a reef. Non-oceanic rock is made up of very different minerals and elements than reef rock (which is calcium based). Many land-based rocks contain heavy metals, which would kill the animals in your tank. Rock from the ocean also has a buffering capacity to minimize pH swings in your tank. pH swings can also kill your animals. Land-based rock does not have any buffering capacity, hence the unstable water parameters Yote mentions. Land-based rocks also can leach nutrients that will cause algae outbreaks, and some contain high levels of silicates which will also wreak algae havock on your tank.