Well a major threat would be the refusal to use the search button. There have been countless discussions to this very subject.
I'd say that the only real risk is a 51% attack. Besides that, the only real threats would be events that could possibly destroy or severely damage our planet/civilization. Something in the lines of a Hypernova in which the gamma ray burst is directed towards Earth. People shouldn't worry about 51% that much, nor about possible weaknesses in encryption, as Bitcoin can always get upgraded/fixed.
I think the biggest threat is the need to make the block size larger. It's not really a problem at the minute but it will be in the future, but I hope its sorted long before then.
Nonsense. That's not a threat at all.
I don't think a 51% attack would be profitable.
Neither were the spam attacks, and yet they happened.
Isp shutting down nodes etc
Governments secretly buying bitcoins and destroying them
Satoshi selling his 1 million BTC
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ISP's can't shut down a node if they do not know that it is a node. Exactly what I'm doing under a VPN, the ISP does not know.
Bitcoins can't be destroyed, but rather abandoned. Even if we are left with only a single Bitcoin, we can divide it enough times for everyone. If Satoshi does sell his stash, that would only have an affect on the price (supply and demand).