We got a Backdoor Hacker AI once and selected two worlds next to each other (one of mine, one of my partner's). Sadly, our defense system was inadequate and one of the home command stations fell (to three raid starships III which came with Exo-galactic Spirecraft wave - I put far too little gravity turrets on that planet).
As we
really didn't want to have waves strike our former homeworld which lied in the deep safe pocket of the galaxy we put Warp Jammer on that planet. And all defenses were moved to the only remaining homeworld as a whipping boy - if Exo-waves can strike through
that wormhole, we
need to be able to protect against it and rare 4 simultaneous waves...).
So yes, there are rare occurences where a Warp Jammer is very useful as you
cannot gate raid and you absolutely want to have the world secured ;-).
In case there was a Warp Jammer structure - an unlockable one, not the Command Station - wouldn't it kind of neuter Backdoor Hacker AI? Definitely it would completely change our strategy, as we'd block waves to our planets and made whipping boys of some front planets instead of accepting the losses of up to 3 planets from time to time (as most fortresses, both superfortresses, most turrets etc were located on the remaining homeworld).
Remembering some of those waves we had and some interesting problems we faced - without this Warp Jammer we might have not won that game. 5k knowledge well spent ;-).