>Ceramic caps, until now, were really big, however, and the
>good ones are expensive.  The not-so-good grades (while
>they have a ton of capacitance) exhibit someweird behavior
>including piezoelectric effect (ie, they act like a little
>piezo transducer, meaning they create a voltage under
>mechanical stresses) and drift with temperature and voltage.

Another nasty trick that some will do is play battery. There were some nasty
ones made in Australia about 30-40 years ago which were good at this. The
higher capacitance and lower voltage ones were the best at it.

I do not know what the chemistry was behind this happening - it may have
been that they had a particularly bad processing facility that did not clean
up after some of the stages, or something like that. I do not know if
current SMD ones have ever been known to do things like this.

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