I think we might miss interesting things if ban particular news sources. And so, I might end up visiting them more just to ensure that I don't miss any news.
To the gentle(wo)men iamelgringo, thanks for telling us that valleywag is a bunch of aho* but that has no correlation with reporting.If people find that valleywag reports are made up, lack substance, people will choose to not go there despite it being posted on hacker news. You want to give the choice to the end user (me and you) to see that valleywag article or not. Why restrict choice.