If Facebook had quit providing any sort of value to the people, had quit providing incentive to store their valuable assets like photos, videos, opinions etc. on their system, then yes, I think if someone copied Facebook %100 and started operating it properly, they'd be a good social network.

Facebook is not just a code or just a network. ICQ had a network. MSN Messenger had a network. Heck Google actually has a network.

But without providing value, a network is not worth a thing.