Not science and technology are threats to humanity. Threats are about sociology. – All of Hawking's threat statements are populist without any substantial analysis and they obscure all real causes.
I use two articles as an opportunity to apply my criticism against Stephen Hawking's positions in sociology. (I criticised already his positions in fundamental physics here.)
Below I comment six of Hawking's statements. 
1. "A superintelligent AI will be extremely good at accomplishing its goals, and if those goals aren’t aligned with ours, we’re in trouble."
Hawking is wrong. He circulates the fairy tales of artificial intelligence as a freestanding autonomous creature. – But the threat to our existence is NOT unpredictability of AI – it is (to the contrary) the clear purpose of AI intended by a strategic calculating clique of humans: low-key, comprehensive totalitarian control.
Of course there will be a lot of amazing relieving applications of specialised AI. But the planned ahead main purpose of AI is to be a weapon itself, the >> ultimate weapon of machine-controlled socialization. Its main purpose is to be the holy knowledge base of truth and the holy legitimacy of last resort.
Long before artificial intelligence would be able to accomplish "own goals" (if ever) it will enable this clique to turn humanity into a "mentally guided" humanity.
Being possessed by far and future superlatives Hawking is incompetent to see how close the takeover in fact is (takeover not by machines but by a well-known globally operating brotherhood).
2. "We will not establish self-sustaining colonies in space for at least the next hundred years, so we have to be very careful in this period."
Hawking is wrong.
First: It will take rather four hundred years from now before exodus from Earth starts (and then another thousand years until arrival). – But that's not the point.
Hawking's reasoning for space travel ("independency and therefore safety") is nonsense in general.
Colonies in space can generally never act independently and "self-sustaining" – for political reasons. I proved it here.
Second: In four hundred years there will be no mankind anymore. "Being careful" in this respect is nonsense. Simply the genes of those who planned the ruin of planet Earth will be fired off then with some starships toward exoplanets. – It is not more than perverted hopes (of criminals) that set forth on this journey. 
3. "Gen tech entails unpredictable riscs, e.g. genetically-engineered viruses."
Hawking has no right to caution against unpredictable riscs of gen tech.
In earlier interviews he suggested genetically-engineered improvements of humans to "stay competitive when colonising the Milky Way".
Dreaming of man breeding for the purpose of being superior to other races (in space) is purely fascist thinking.
4. "Progress in science and technology becomes an ever greater threat to our existence."
Hawking is wrong. Technology in itself isn't a threat. Threat is about sociology, the social system, not tech. Technology is only a threat in the hands of an uncontrolled system (like U.S. capitalism).
You should ask: Who built the first A-bomb, who built the first A-submarine, the first laser-guided missile, killer drone etc.
You should ask: Who converts today his arsenal into tiny tactical A-missiles, so nuclear weapons can be used without calling it a nuclear war?
Who works on new weapons like genetically engineered viruses? Who dreames of cyberwarfare, of autonomous killer robots etc.?
5. Hawking speaks of "disasters" that can happen to humanity.
Hawking is wrong. What happens to humanity is NOT a "disaster" (that "happens" accidentally). – It is planned ahead (or at least they hazard the consequences) by for-profit companies, by political interests.
Hawking is right in the one part of the issue: the U.S. ideology will prevail globally.
But he is wrong in the other part: that that would be a good thing (to sacrifice planet Earth for profit and global dominance).
6. "Global warming is one of the greatest threats facing humankind."
Hawking is wrong. Global warming isn't a Biblical Plague. Global warming is the consequence of a socio-economical process (of unregulated competition in the world economy).
The real question is (as an example), who uses the world's oil consumption as a weapon? Who manipulates the oil price by surplus production?
Henry Kissinger did manage in the 1980s (by a Saudi agreement) to ruin the Russian economy by low oil prices.
Today they try the same again by abruptly exploiting U.S. shale oil to a huge extent and by lifting the Iran sanctions at the same moment. – No matter whether it ruins all efforts to stop the world from burning oil.
Stephen Hawking is too narrow-minded to see this is criminal politics and not abstract "global warming", not "human nature" or what ever he thinks.
My conclusion: Stephen Hawking's threat statements are populist without any substantial analysis and obscure all real causes. (What a disturbed person.)
 I migrated my article from Google+ (an online service that is closed now).