2010/2011 time frame. Google and others helped sink the traffic, all written up at apnic labs. It's how 1.1.1.0/24 got held back from general release.
e.g. https://www.potaroo.net/studies/103-slash8/103-slash8.pdf and https://conference.apnic.net/news-archives/2010/network-1/as...
e.g. https://www.potaroo.net/studies/103-slash8/103-slash8.pdf and https://conference.apnic.net/news-archives/2010/network-1/as...