For what it's worth, the somewhat hilarious reason justpaste.it is on the list is likely that it used to be a favourite of Islamic State terrorists a decade ago. https://www.politico.com/magazine/story/2014/08/islamic-stat...

Googling 'site:gov "justpaste.it"' also brings endless results of government documents mentioning the site in the context of terrorism.

I somewhat doubt US immigration authorities thwarted any would-be terrorists by asking for their justpaste.it username, but what do I know, perhaps this was an important breakthrough in the global war on terror.