A quick search for found a lot of articles which mention MN, and while most publicity is good publicity, it does seem a bit cheap for journalists to pull a few comments out of a thread and use them without any reference.
It would be quite easy for them to pay a fiver for a year to at least have the courtesy of sending a message to say "We're running a story on 'xxxx' and plan to include your comment" and at least allow a couple of days so the poster has a chance to comment back to the journalist.
Of course, it would be nice to get some sort of agreement from the founders, too, but the way that comments can be used is perhaps not always flattering, so I guess the journalist's idea is to claim "posted in public" and that copyright exists over complete threads, but taking a few extracts does no harm...
Came across board statistics while I was looking at places mentioning MN (and NewsTIN {'tin' was a unix news reader in the 80s, which might be the reason for the name}).
A search for Mumsnet on NewsNow.co.uk came up with only two items, both Daily Mail "This week on Mumsnet" entries - NewsNow searches only the headline text, NewsTIN shows articles with search terms anywhere in the page...
(I stopped looking at the articles after a few pages, but seems most UK newspapers include mentions from time to time - just wish I could get similar publicity for my website about slow broadband speeds!)