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You see there was this rare weather phenomenon in LA when double rainbows showed up in the sky. And the people of LA flooded twitter with the pictures and the tweets. Pictures were uploaded from locations ranging from skyscrapers, tenement buildings and parking lots. Hence the inclusion of the term in the world wide trending topic. This is significant as twitter recently tweaked its trending topics algorithm to consider a spike in discussion while including the topic on the list. The algorithm was so fool proof that even Wikileaks did not manage to cope with it.
source: http://tech.gaeatimes.com/index.php/archive/wikileaks-barrier-broken-by-double-rainbow-on-twitter/