Until now. I got a set in which one of the bricks was malformed. It looks like not enough plastic got injected into the mold. Obviously, this is an extremely rare case.
What am I going to do about it? Nothing. I can easily replace it from my large collection of bricks, and it's actually pretty cool to have something like this; it's a bit like looking at an X-ray of a brick. And because it doesn't have any extra bits of plastic sticking out, it can still fit into constructions like a regular brick. Thanks, Lego!