Personally I felt really abandonned by the DIG for migrating to FB instead of using it as a supplement. All of a sudden, within a few days, the chat thread was empty (you could hear the crickets) and even though some of us voiced that we couldn't/wouldn't move to FB, hardly any of the original group came back to chat with those of us left behind. I had been really looking forward to having a DIG when I fell pregnant this time and I felt really disappointed when the group disappeared and I no longer had that support network.
BHEDITOR - to answer your OP. I chose not to move to FB because I want to keep BH separate from my real life. I use FB to stay in touch with close friends and network with colleagues. It isn't really a space I feel comfortable mixing with my on-line version of myself (through which I reveal all kinds of personal things I'd never share IRL). But in choosing not to move, I basically lost my Due In group, which was a disappointment.