xD, We're all gonna die ... The sattelite'll hit into some island causing it to collapse into the water triggering a catastrophic release of energy resulting in the biggest tsunami ever recorded bringing with it a host of natural and ecological problems killing millions and leaving the earth in a useless waste heap. Then, Cloverfield'll come and wreak MORE havoc ... AND TOADS WILL BECOME EXTINCT! (No, pun intended Sixty) AND THE Common man will rule the EARTH.
No but seriously, if the satellite doesn't burn up upon re-entry of the earth's atmosphere, there could be a possible problem if the satellite hits the suface of a body of water with enough force. We could be looking at a possible super-tsunami ... O.o