There is a scene in Captain America, about sixty seconds long, in which all
three major characters do something criminally stupid.

In this scene, Howard Stark is showing the Captain some new equipment,
including a selection of shields, at least three, seemingly the size of
refridgerator doors. Before Stark gets even one sentence into describing the
first shield, Rogers asks about a smaller, circular shield sitting on a shelf
under the table with the other shields. Stark says "No, that's just a
prototype" but Rogers presses him on it. Stark explains it's made from
vibranium, a metal stronger than steel, but a third of the weight. "It's
completely vibration absorbent," Stark explains, but hard to get. "That's the
rarest metal on Earth. What you're holding there, that's all we got." At this
point, Officer Carter enters asking for the Captain's attention. Rogers,
holding the shield, says "What do you think?" at which point Carter grabs an
automatic handgun and fires multiple bullets directly into the shield, which
of course ping off and fall to the ground.

The entire clip is found here:
http://www.youtube.com/watch?v=baEP7JpNFeE
It lasts 53 seconds.

Holy crap. Where to start?
A) First and foremost, clearly Steve Rogers is even more of a dick when it
comes to the R&D people than James Bond on his worst day. Howard Stark is the
best mechanical genius known to America and he doesn't want to hear a single
word he has to say about the inventions he intentionally made with the sole
purpose of saving Captain America's life. For all he knows, the first shield
is made from adamanium, has an IFF chip, and dispenses food and vaccines to
homeless children. And, when told the item he picks is "just a prototype" he
continues to press for information about it, rather than "oh, I should hear
more about the completed models he clearly built personally for me." And why
he would go out of his way to pick the smallest shield is beyond me.
But Rogers turns out not to be the worst offender. Stark is far worse.
Apparently, he has the US's sole supply of vibranium, and has made it into a
shield, brought it to this demonstration -- where they US's only shield-using
soldier is waiting for new equipment. And he has NO INTENTION of showing this
shield to Rogers.
C) And besides this, while I'm 100% willing to accept the sci-fi properties of
vibranium in a comic-book movie, and it sounds like a wonderful property for a
defensive item, it sounds like the worst possible choice of material for a
blunt weapon. Captain America spends the majority of combat in the rest of the
movie using the shield as a throwing weapon, as well as beating people with
the edge and face of it. Based on what I can see of the shield, it is AT MOST
30 inches across and a quarter-inch thick. A disc of steel that size would be
just over 51 pounds, so the shield he's holding weighs about 17 pounds (and,
realistically, is probably thinner and therefore even lighter). Even if the
metal is being overstated by Stark and is, let's say, "only" 90% vibration
absorbent -- still easily enough to stop 0.45 bullets at point-blank range
with no risk of injury to the user -- hitting someone with that would have the
inertial of using a 27.2-ounce weapon. I grabbed a 0.45 ACP handgun at random
from Dick's Sporting goods website, and it was 28 ounces. The Captain would
literally have greater effect throwing his SIDEARM at Nazis.
D) As a followup: Stark is a world-class genius at designing weapons and
armor. He had even built and brought Captain America's new battle armor to the
very same demonstration, while hinting at its possible inadequacy. Exact
quote: "Carbon polymer. Should withstand your average German bayonet,
although, Hydra's not going to attack you with a pocket knife." So, given
vibranium's shortcomings as an offensive weapon, why not use it to make a
helmet and/or chestpiece? He does use metal armor under his uniform in the
comic, so this isn't asking too much. There seems to be enough. Then you can
make the shield out of titanium -- also stronger than steel, but lighter. Or
titanium carbide, which is even harder. Yes, it's true, the real Captain
America in the comic used a vibranium shield in WWII, but you'd think there'd
be a better explaination than this!
E) But as bad as both Rogers and Stark are behaving, they can't match Carter's
behavior. She enters the room a full 10 seconds after Stark describes the
metal's special powers. Now remember: this is "just a prototype" and he had
shown no desire to show it to Rogers, having made other items specifically
instead, and therefore, it seems unlikely he would have explained it to Carter
either. So when she grabs a pistol --
F) And JUST a second. Who leaves a loaded pistol with a round chambered and
the safety off just lying around on a table?
E) -- and she fires it directly into a hard, metal surface. Based on earlier
scenes, I have no doubt Carter could easily shoot the shield at that range,
but how did she know this would be a good idea? For all she knew, the shield
-- clearly lightweight -- was a mockup of aluminium, and the 45-caliber
bullets would have ripped through it and killed the clearly unarmored Rogers.
Or maybe she trusted Stark would have brought a bulletproof shield, fair
enough, but what about the obvious danger of a ricochet? The room is crowded
with unarmored, unsuspecting officers and scientists. Stark himself is
standing literally four feet away, at an angle where a bullet could very
realistically bounce off the shield and hit him square in the torso. Carter is
clearly some kind of sociopath whou should never be allowed near weapons, or
maybe near people, ever again.
G) And finally, while the bullets do fall harmlessly to the ground -- which
vibranium should have done, so full credit there -- they also hit the shield
with a *ping* sound audible over the gunshots. Sound, as in vibration.
Clearly, the material's not living up to its name after all.

Shinarae "more of a DC fan anyhow" Lluminus