IMHO frid.ge was always a bit questionable, I personally built a comparable product and quickly realized that there is a huge amount of momentum around getting people into a system that is pretty much devoid of people you know.

Groups (and Events) are two features that Facebook has left somewhat sidelined over other feed oriented features. If they can get the mojo right on Groups then whole classes of me-too features (like frid.ge) are somewhat suspect. The interesting question is can you have a group that's coworkers who aren't your Friends, thus digging into Yammer is a serious way.

I'm not sure that it has. Facebook will move slowly to add features since Groups isn't their core offering (and probably never will be). I think it'd be quite easy to differentiate yourself from Facebook Groups if you focused on adding features Facebook will not or cannot add (such as file sharing, legal or otherwise).

I would hope not. It's been one of the biggest complaints about facebook. If you're starting a social network I would hope you'd be prepared for competition from facebook.

Probably, along with a ton of other me-to niche social networks.

If I ever happen to create groups(i am not sure yet) , I would prefer frid.ge