It seems like there is a large strategic advantage in generally avoiding contact with other civilizations (with caveats).
After full-annexing one neighbor, the Blorg got a large Threat modifier (equiv. to AE/infamy/bb/whatever) with all their remaining diplomatic contacts (smaller for non-adjacents, of course. By about half.) All those contacts then joined an alliance together.
But when the Blorg encountered a new contact, the new contact had no Threat modifier (and it was just as close to the Blorg as the other non-adjacent neighbors).
Further, the Blorg received no benefit from being in contact with all of those neighbors. I suppose they could designate them Rivals for the purpose of generating Influence, although even one or two adjacent rivals seemed sufficient what the Blorg were doing. Maybe a lot more resettlement could have required significantly more influence. But it's not like the Blorg were trading or otherwise dealing with those non-adjacent neighbors, whom they now have to fight in their next war.
Maybe the fact that there's limited choice in contacting non-adjacent neighbors means this is a moot point. A couple times, the Blorg were contacted via some kind of MTTH-delayed "adjacent to adjacent" contact. But regardless, it makes the game much different than, say, EU4. Imagine if in EU4, you didn't start with knowledge of your own continent. You could freely conquer everyone around you, only causing AE with people who knew you existed.
But regardless, I've started to have some doubts that this game will actually be very fun, because the number of other "players" (AI or whatever) is so small in the early game. And Martin said they were playing with a very high number of empires for the size of the map. If this is a "crowded" game, I can't imagine how little there will be to do on a "normal" map.
My other concern is that there is a lot of pointless clicking to upgrade planets, even on the limited number of home systems the player controls directly. Instead of thinking that every planet is like a province, we should be thinking that every planet tile is like in a province insofar as the number of clicks it requires to manage it. Development+estates in EU4 is already a nightmare of pointless yet mandatory clicking, and Stellaris is starting to look just as bad, if not worse.