Satoshi posted about this concern:
http://bitcointalk.org/index.php?topic=241.msg2071#msg2071Yes...
But what you describe is only possible after someone have noticed and prooved the network split is happening.
Do you propose any method to detect the beginning of the network split?
You think people would fail to notice an entire ISP/country/continent falling off the Internet?
Why do you think, that what you describe will be the only reason for a Bitcoin network split?
And if some people will know that a continent is disconnected, then why all others will be as informed?
And even if everyone will know, that some amount of Internet is disconnected from the rest, then
how would they decide whether that is a good reason to stop processing (and sending) transactions?
ISP disconnectivity is not a rarity today, single misconfiguration may shutdown routing for a whole AS.
Will that be enough reason to stop processing transactions or not?
The same with a country and continent.
The question is not wheter there exists some parts of Internet or Bitcoin network, that will reconnect later.
You may always answer YES here, at every moment they exists. My phone loses signal very often, for example.
The actual question is
Whether I am connected with a network, that will be a majority of nodes on reconnect, or not?
It is not possible to give a definitive answer about future, but you may estimate that almost accurately based on the size
of the network before the split and the size of the network after the split.
If your network is not going to be a majority later, then it is safer to use another payment method, I suppose.