I tried to start this the other other day but couldn't work out how to add my screen shot. I think I've managed it now. Anyway, the point is ...
I've just realised that the first page you reach on Mumsnet now looks like this (screenshot below) so that your options to get to the next page and start talking are only 1) active or 2) AIBU. Why can't you see an obvious way to a full list of talk topics, or even popular topics, on the first page? Why is AIBU the default?