Friendly players that include me in their activities. When I first came home, I found many old friends from retail, and we "got the band back together". We founded a SG, created/equipped a base, and played regularly for the first 6 months. Then they all got bored and left.
Well, almost all. A few of us are still playing, but we've all gone our separate ways and are doing our own things. It just became simpler/easier to create my own SG and base for all my alts. Having a roomful of teleports and storage units is too handy to pass up or leave to the whims of people I don't know/trust.
While I've had no problem finding teams, nobody ever talks about their SGs any more, or tries to invite others to join them. It seems like everyone is doing their own thing, and we're all doing the typical MMO thing of "playing together, alone". If they've got a good SG, they're keeping it to themselves, or they're like me and simply don't have a regular community of their own (like me).