Has anyone seen a work social network that wasn't a joke? We have one, and the only use is that your director/VP asks their org to follow them, and then posts various strategic stuff they want you to see. There's zero peer-to-peer usage at all.
For a social network to have value, you need users who are compelled to frequently submit content. By adding a power structure, users have to evaluate their decisions, which can generate anxiety or extra work, leading to a drop off in contribution rate.
It's one of the reasons teenagers ditched Facebook once their parents joined.
So we'd have one for the Project X team discussion, and another for Project Y team discussion, one that included the QA team if we needed to discuss bugs with them, and we'd make a temporary one if we just needed to discuss prep for an upcoming meeting, etc. And then we had the group that wanted to share meme pics and youtube links, and the group that wanted to share links to metal music, and another to discuss anime, etc.
You could also put in filters so it only notifies you if certain words appear in the chat, like your name or some feature you're in charge of. It was simple, dynamic, and more effective than any other company I've worked for before or since.
One of the bigger issues with the tool, however, is adoption. Maybe an enterprise facebook would have a higher usage rate because everyone already knows how to use it?
If everyone actually used the official collab tool here at gigantic_company it'd be a lot easier to find out if another department already solved your problem so you could learn from their implementation, rather than relying on the tribal knowledge of someone who's been here for years and years. I'd like that.
Most communication happens in Outlook/Exchange mailing lists.
I do think that Yammer and it's ilk offer somethings that plain email don't - better attachment integration and history (with email you can't see discussions that occurred before you joined).
One thing I don't like about Yammer (and other social networks for work) is that discussions are very "flat". Contrasted to email discussions at my work, which can get very lengthy and include many branches. They wouldn't scale to Yammer at all.
For smaller companies where all employees are in the same place I guess it wouldn't have as much value though.
I can always then connect it to Salesforce and any other third party systems via Zapier.