For instance, I read this story earlier on Variety and it was presented as fact. If you go back to the same url [2] the story and headline have completely changed.
Previous Headline: Cable Operator Snafu in Boston Leads to Porn Airing on CNN...
Current Headline: CNN, RCN Deny Reports of Porn Airing on Channel in Boston
[1]: http://www.snopes.com/cnn-half-hour-porn/ [2]: http://variety.com/2016/legit/news/cnn-porn-boston-rcn-cable...
But according to the content page, Snopes does't know. It's probably or most likely false but CNN and RCN are still investigating, so we don't know for certain.
But just as some news are keen to run with any rumour as news, Snopes seems keen to mark rumours as False as quickly as possible for the same reason; put content online that gets clicks.
According to these articles, there was porn on CNN over large parts of the east coast, for 30 minutes. 30 minutes of porn on CNN in significant parts of the US, on Thanksgiving evening, and only one person noticed it and decided to post anything about it online? That smells very suspicious.