Another thing, about cloaking devices. Why are they never used to maximum tactical advantage?
Remember the old Star Trek series, where Kirk was always against the Klingons? Why did the Klingons never send a fleet of cloaked ships to carpet-bomb the Earth? Or even destroy the whole planet - planetcracker bombs were possible with antimatter, it has been done before. Fly one ship in, cloaked all the way, (have to uncloak to fire weapons) BOOM, no more earth, cloak and leave.
If you're going to make a bad guy that is smart enough to develop invisible ships, you can't make him also dumb enough to ignore tactical advantages.
Same goes for the Romulans. They are much more clever and they have cloaked ships and they have a major chip on their shoulder for the Federation. Long before the ST:TNG tachyon sensor grid they could have sent one cloaked Warbird to Earth, one to Vulcan and blown them up. Why did they not?