I have no idea if it's a google ad - it's one of the ones that are over there ----> above the 'Mumsnet latest' stuff.
I couldn't quite believe it was real when I read the blog, so I went and had a look at their site and it turns out it's 100% real. So perhaps that's why it came up here as well, if it is a google ad. Anyway, if there's anything you can do to stop them appearing on MN, that would be great.