I only saw it once, and I had just clicked on a thread so the page changed. Despite refreshing quite a bit I haven't seen it again. It seemed a bit wrong. There was a bit that said "Who makes the decisions? You? Your partner? Both?" and then there was a bit underneath that said "Mumsnet survey" but it didn't look at all official, no MN logo or anything. There was also a name, that might be a company name, it was either UMUM or UMUN (I think).
Sorry I can't give any more detail, I just caught it out of the corner of my eye. I'm just a bit worried that a MNetter might give personal info to a company under the impression that they are doing a MN survey.