This happened to me a few times too. It would literally take a second to add the name of a news source to a list whenever the admin adds it to whatever line of code blocks the posts. Even if the list was just a single text file with the names of the blocked news sources in alphabetical order.
I have to agree. You could even use an XML file and search it. That might be easier than using INSTR on a MySQL field. I imagine the list is shrinking as media companies shrink.