Hypothetical situation: the Internet gets split in two, what happens with Bitcoin?
Any of the "pirates" with nodes on both networks and who have unspent coins in the blockchain before the split would be able to spend those on both networks, for as long as the network is split. 

Upon joining again, the longest chain will always prevail. So anyone who mined any new coins after the split and those were mined on the shorter of the two chains will lose all those new coins -- they will become invalid. 

Anyone who spent coins that existed before the split, but spent them only on the shorter chain, will have those coins returned to him/her after the join, because they were only spent on the shorter chain (which is discarded and invalidated)

In short, the bitcoin network will take it in stride :) but some people will lose, and some will benefit doubly.