I can't understand this behavior, or why it hasn't been addressed yet 
Often in my games, inevitably all my closest neighbors park their entire fleet in my borders and hover menacingly over key planets and starbases, shadow my ships etc. At first I was impressed, and thought an imminent war declaration was incoming, but I've played the game far too long now to be taken with this behavior.They rarely (if ever) declare war. They just like to sit.
It's to the point now where the AI's are often being ransacked by other (further away) AI powers, and yet the entire (closer) AI fleet just sits around hovering within my borders, not even a though towards defending itself?
I really think the AI needs to be taught about borders, and an invasion of space should only be considered if the AI actually intends to declare war. This space loitering is crippling to the AI's closest to me. Further, if it's under attack, and is losing starbases / shipyards etc (lets face it the AI cant actually invade planets yet) it needs to divert its space loitering priority to actual defense of it's empire.
please