Can the blockchain ever be restarted? Since full nodes must store the entire blockchain, and it seems to currently be 9 gb in size, it seems that sooner or later, it will be too large to handle ( if 9gb isn't already absurdly large ).  Is there no provision to ever restart the chain?  Certainly it can't just keep growing for all time?

It seems to me that sooner or later, a second genesis block will have to be created and unspent transactions will need to be converted from the first generation, then new transactions to the first genesis rejected, before finally discarding the first chain once all unspent transactions have been converted.
That's probably not gonna happen. The only way restarting the block chain without losing the distribution of coins would be by hard coding all the unspent outputs from the moment of the reset in all Bitcoin clients.

If you say


  Certainly it can't just keep growing for all time?


Why can't it? If the block chain grows at a slower pace that the price of storage, which can be predicted by Moore's law, why would it matter? Also, Bitcoin will probably evolve to a situation where not every user will have to keep in sync, but will use a service wallet or another payment network backed by Bitcoin so that it doesn't need the data.

Also, old blocks can be compressed when you don't use them, so the blockchain size can be reduced a little if it becomes really big.