Me and Deus Ex (you might know him) were planning a joint attack on a guy called "5150" because we were on the same team on multiplayer. So he had his huge fleet with a Dunov, Kol, 4 Kodiaks and of course a whole load of frigates etc placed at a gas giant one jump from 5150's planet Giomon I think it was, and I had mine on an asteroid belt the same distance from Giomon as well. We jumped in at the same time and began firing on the sparse defenses. I immediately set the single capital ship Marza on bombarding the planet while my frigates and Hoshikos went for the defenses. However, a huge fleet of 5150 jumped in from an adjacent Terran planet and we were forced to engage them. We got lucky when a pirate raid began on Giomon and distracted his forces. We took this opportunity to jump our fleets to that now-undefended adjacent Terran planet and I managed to wipe out the colony, however his fleet took care of the pirates too quickly and came back for us. We were forced to retreat with a minor victory.

I think the problem here was is that he had too much intel on our fleets waiting to attack, and positioned his on the Terran planet to surprise us. He didn't expect the pirates and even offered a cease fire in the middle of it, but still managed to beat us because he knew we were coming. The reason for this is that we had allied with the 4th player, who 5150 was also allied with, and therefore could see our fleets coming.

I guess the lesson is that no great surprise attack will work when the enemy sees it coming, lol.