Great thread, everyone.
I am reminded of Avengers (vol. 1) #28, wherein the Living Laser melted the "special alloy" off or Cap's shield, and eventually disintegrated it. Later that issue, Cap appeared with his shield, perfectly unharmed... "special alloy" intact.
In the first few Cap issues of the Avengers, Tony Stark installed magnets and special circutry into Cap's shield, which allowed Cap to control it by remote-control. No mention of how Tony was able to hollow out room in the indestructable disk, or why Cap didn't just use his fabulous skills with the disk like he always used to. A few issues later, this whole canard was dropped in favor of the ol' reliable skill and training explanation.
During the Secret Wars or something, when Cap was off-earth, somehow he lost his shield, or the Beyonder destroyed it or something. Through sheer force of will, he re-created it, perfect in every detail. Despite the fact that nobody alive knows the precise chemical makeup of the disk... and I'm sure Cap has no idea how to make Vibranium or Admantium.
Not dreams, not imaginary stories, still considered in continuity I believe...
The point is, you never can tell what something can or will do. You may need at least 50 writeups of Cap's shield just to get it right, considering the butchery of horrid writing and catastrophy of dreadful editing that goes on from time to time.