I think you would find it advantageous to at least store the most important header information (Subject, Date, Author, possibly threading info) in a database.

You're bound to need searching for that specific piece of news some time later. The more news there is likely to be, the less efficient will it be to search through a bunch of unindexed files.

Also note that if you have the whole article in a MySQL database, you can enable full text searching over the article, which can also come in handy.

And I don't believe that storing articles in a database is going to eat that much more space than storing it in individual files would have.(Unless you compressed the files, which would make searching through them even more difficult.

Consider this: Diskspace is cheap and getting cheaper every year. Your time isn't.