I have reservations, myself. I used to be a regular on Babyworld - you could access all areas (they later changed it so that certain topics were member only: Losing a Baby, and Pregnancy After Loss) but because of the site layout you tended to stick to certain topics. There was little interaction between topics and thus the groups got very insular.
For example, I posted a lot on the SAHMs board - now I am a SAHM but that's not all I am. And the only time there was any dialogue between the SAHMs board and Working Mums board was when a massive row kicked off. One of the things I love about MN is that I get to hear so many peoples' opinions - not just people who are in a similar situation to me. If MN was run along the same lines I could restrict myself to reading/posting on..chat, other subjects, behaviour/development, in the news, health, food...But I'm bloody nosy and I want to read about everything else as well. Though I do find the sheer size of MN overwhelming sometimes I tend to treat it like a precipice - I don't look down!
Another example - there was a Special Needs board on BW but it felt very closed. I never went on it. Now, I don't really have any reason to read or post on SNs here - but I feel I have learned so much from doing that, and have a much greater understanding and empathy with parents who have SN children than I ever had before. I used to see children behaving badly in shops and tut tut (inaudibly - I wasn't that bad!) to myself. Now (thanks to jimjams et al) I think "I wonder if that child has autism, Asberger's" etc. I smile at every baby/child I see who has Down's because I always think of TC's Lottie. I put money in CP boxes and buy Scope Christmas cards because I think of lou's youngest ds. If I used an ignore function on the SN threads (and, in theory I should, I have no " reason" to read them) I would miss all that.
I don't breast or bottle feed, I'm not pregnant or TTC, I'm not part of a multicultural family, or a bilingual one, I'm not a student parent, or a lone parent...I could go on but I won't. I have read and /or posted on all those topics, and "met" people I wouldn't have met otherwise - I guess you could call it sticking my oar in but I don't care.
I have learned so much from MN, and heard such varied experiences and POVs - I don't want to restrict that at all. And I think it would be very sad if MN became like Babyworld - where posters tend to stick to certain topics and there is little cross-fertilisation. It's very isolationist and gives a distorted picture of parenting and the world in general.
Anyway, if it happens it happens. But I wanted to put my two penn'orth in (as ever!)