ha ha, but you don't post later than me tonight, nightowl. Poor me, usually posting early in thr morning, late at night or at weekends - I miss lots of juicy active conversations that way. It's a wonder anyone talks to me at all!
I find the best way to get an overall view of mumsnet talk it not to click on the active conversations threads but scroll down all the days' threads.
I can feel so guilty when I don't finish posting on all the threads I want to at a given time. I see threads I can relate to, people I really want to say something to, but whizz past without stopping, yet post on others. Then agonise that if 'x' sees I've posted today but missed her thread out, will she think I don't care or I disagree? In all probability, 'x' is totally unaware of this. But I wish there was some shorthand for saying 'read your thread, want to say something but run out of time'.
I do think more groups are forming on mumsnet, just because it's so big and people have to choose which threads to read and reply to. I haven't come across any thread discussion that makes me feel positively unwelcome, though.
I quite enjoy breaking into different threads with people I don't recognise, and when I have the time (which sadly is rare) I try to do this.