They cited 'too busy' when they closed the Woman's Hour message board.
They cited 'cost cutting' when they closed the general R4 message boards {though not mentioning the fact that TA board was not going to suffer any cuts}.
They ignored the suggestions that they could co-opt volunteers as moderators, in favour of keeping everything 'in house' (but not being able to really afford it, 'cos they waste so much cash on 4 revamps {or more} of their whole damn awful website, brought in 'Blogs' {which is a one-way thing, and carefully censored moderated, unlike the MessageBoards where anyone could start a fresh topic}).
Sorry for the little rant but they have had daft experiments like using live video streaming for some R4 and R5 shows when the medium is RADIO, and played with silly changes to integrate iPlayer access (making 3 clicks to hear something about 5 or 6, if it works after all that).
I lost patience with the BBC and their 'messing about' from 2007 to 2010 (and later, perhaps) when they had some (self proclaimed) 'radio futurologist' who used to work in advertising for Virgin Radio and then set up his own radio, TV, newspaper index site, and then closed the forums from the general public, only allowing those employed in media jobs to view/post. Then he screwed the index up by making it tie into f^%$#g Twitter and Facebook. Anyway, I've no idea how much they paid him to 'consult' but bet some pet projects of his became BBC experiments, with little or no benefit to the TV Licence payer.
Anyway - the MessageBoards have always had a few problems, and excessively strict BBC staff as moderators was one of them. I think an overspend of 125 million one year on the BBC website is something that means not having voluntary moderators is a wasted opportunity to have redeployed those who had been moderating into more useful activities, such as checking the contributions on the BBC News pages in their 'Have your say' section, so it didn't take up to 15 hours for comments made by the public to be displayed.