The state can also seize bitcoin. That is what has happened with funds the Feds claim were profits from drug dealing on the Silk Road. Depending on your jurisdiction, they may be able to compel you to give up the passphrase to your wallet. If someone installs a keylogger on your machine, they may be able to seize it too. Nothing is perfectly safe.

If a consortium of Google, Microsoft, Amazon and other big names decided that crypto-currencies were a good idea and that Litecoin was their crypto-currency of choice, then I suspect Bitcoin's value would evaporate quite quickly. I mention those guys because they have big server farms that could use spare capacity for mining, there-by preventing anyone else mounting a 51% attack and also making themselves some money. Litecoin's hashing algorithm would probably suit those server farms better than Bitcoin's would. Even if they choose not to follow this route, you know they are thinking about it.