Dan, please don't take this wrong but HOW? I'd really like to know. Is it from the vinyl expanding and contracting?
Plus, I've always been told to put tape on glass to keep it from breaking. Wouldn't the vinyl act the same?
Sheeting the window with black vinyl is a cheap way to prevent any way of seeing through it. It's cheaper than opaque window film and more opaque than a curtain. The black vinyl will absorb the heat from the sun thus causing the window glass to heat up and expand, thus causing the window to explode if the window frame does not allow for the glass to expand. Like they mentioned above, the amount of coverage that is on that window will no way do such a thing. If I had to guess I'd say about 75%+ could do such a thing, provided like also mentioned above, there are no rubber seals to absorb the expanding glass, but that's just a guess.
The vinyl (or tape) wouldn't do anything to keep it from breaking at all, all it would do is hold the pieces of glass together in case of a full blown shatter.
The proper way (but not most cost efficient) to opaque out a window is to use commercial opaque window film that will "reflect" the heat and not "absorb" it. Vinyl will absorb the heat, not sure if reflective vinyl would or not, but I'm not going to test it =)