Arguably all hackers should self destruct after a successful hack, as right now they can be used as half-arsed scouts - not displaying numbers, but giving planet vision of whatever planet they are on, and unlikely to be destroyed unless something tachyon capable comes along. Of course, unlocking more scouts is fairly cheap and it is better, so this is not a major concern, but still.
Even worse, arguably, is that it doesn't really cost anything to create the hacking units, and that they do require a bit of damage to destroy for the AI, so theoretically somebody with way too much patience on his hands could spam such purely as damage absorbers. I have not tried this, but it should be possible with the current functionality where you can just spam hacking units and leave them in place until destroyed.
...I really ought to test this.
