Good points, but what's the alternative at this point?

Because of network effects, more users is generally more interesting. Blue Sky has "enough" at this point for me to be happy there. Programmers like antirez, my bike racing people like inrng, my city's mayor and one of our city councilors, and also a bunch of urbanists.

Edit: you lose some connections moving around, but I've also had friends I've known since the days of IRC. I think I'm mostly resigned to picking whatever works best in the moment and being willing to move (like abandoning Twitter) when it's not working.