Well, true, it's the whole spear and shield conundrum to begin with now, isn't it? You can make an impenetrable shield but then I'll just go find an unstoppable spear, in which case you will need to tape plate carrier armor to your shield to reinforce it, in which case I'll lob the spear from a rail gun, in which case you'll need to put an IPS system on the reinforced shield, in which case I will invest in a sensor jammer, and the conflict just keeps escalating from there... the problem is what you get when dealing with unpredictable actors behaving evasively and trying to overcompensate for the other party's evasions in a quest for an unknowable objective. Basically, it's like war: I build a cannon so you build a bigger one, so I install recoil cylinders so you build a trench, so I build a tank and you make dragon's teeth, and so on and so forth. :-)