Starfleet is pretty much the well-known big boy in the quadrant. They've got sharp minds, research and development, personnel, ships, technology, and all kinds of cutting edge offensive systems. Their defensive technologies, however, leave a little to be desired.

Let's take our classic Galaxy-class starship. The title of "Galaxy-class" tends to spark some imaginations, such as "effective on a large scale." Not so. Captains like Picard are always encountering pesky, problematic species who like to shoot first and ask questions later. Starfleet, on the other hand, has a policy of 1) opening a communication channel first, then 2) performing a tactical analysis, followed by 3) holding an informal conference on the bridge with all senior staff regarding the next action to take, and finally 4) looking for a nice brilliant-idea-at-the-last-minute hack that might allow the other ship to be defeated by a long-distance mind meld / improvised Jedi mind trick / poker face over the viewscreen / power failure induced by quantum radiation-of-the-week / other technobabble.

And while all this is happening, the ship is getting hammered by fire from the other side. Lights are going out, people are rocking in their chairs out of sync, Engineering has yet another coolant leak, and Worf reports the inevitable:

"Shields down to 68 percent!"

And that was on the first shot.

The Enterprise needs an upgrade. It just seems like in the twenty-fourth century, Starfleet should put more effort into developing better shielding systems since the captain will order auxilary power to be diverted to the forward grid after a few random shots from the other vessel ... and it still won't help.

For example, 400 GigaWatts of "particle energy" takes down the shields completely:

Since an omnipotent being was behind that one, we can understand that. But a Romulan warbird running a few choice shots against maximum shields to our hero crew in "Tin Man" reduces shielding to thirty percent? That's rather quick, isn't it? What's covering the Enterprise - Saran Wrap?

In "The Best of Both Worlds," the big E encounters the Borg again, except this time our bold crew is ready with shield mutation techniques ... which of course doesn't last more than a few seconds. The scientists in our research labs apparently need more coffee, because after the modulation failed, the Borg drained shields in no time like they were slurping up iced coffee on a summer day:

Don't mess with the Tamarians when you're face-to-face. If you're Starfleet, your forward shields will be gone with just a few shots, as demonstrated in "Darmok:"

And if you're a Starfleet captain, you must always remember that green = bad. Klingons, Romulans, the Borg, and just about any other adversary seem to favor green weapons. If you see Tie Fighters, it's time to run.

Oh, and Jean-Luc, there are going to be times when your shields will turn against you, like in "Hero Worship." If you see this big bubble of gravitational wavefront approaching you and it grows larger the higher you up the shield volume, you might want to leave the area.

And then of course, there are times when shields won't do jack for you, like in "Relics" when the ship was in danger of solar flares. If only that metaphasic shielding could have been available earlier in the sixth season...

Sometimes, it's okay for the captain to make a suggestive log entry along the lines of, "...if the shields held for another five minutes, half of my crew would still be alive..." Then perhaps someone at Starfleet weapons reseach would get the memo.