I think the best way to strengthen Bitcoin against attacks is for it to become a more useful medium of exchange.  Namely, to be accepted for payment for a wider selection of goods and services.  We have a long way to go, but if Bitcoin were accepted as widely as PayPal, there would be substantial pressure against shutting down the entire network.  Too many jobs and businesses would depend on it.
PayPal processed donations for WikiLeaks, but the Feds didn't shut down the entire payment processor.  Certainly governments will pressure exchanges and other centralized components of the bitcoin community, but peer to peer means new components will spring up to replace them.

Broader acceptance of Bitcoin as payment also strengthens the infrastructure.  It means more network peers, more mining, more exchanges, more smart developers improving infrastructure.  I keep coming back to the first answer to the FAQ, "How to help Bitcoin?": "offer Bitcoin as a payment option at your web shop or service."