Not on my watch, it wasn't. The plumber who came around to give me an estimate initially thought the pipes might have frozen when he talked to me on the phone, but when he looked at it, said the pipes are just old, and that it's not unheard of for "M" grade copper pipe to fail after 40-50 years.

Here are a couple pictures of the leaks I took. The first one is in my basement where pipes are exposed, the second is from my kitchen where a big section of ceiling was cut out for access. It seems to me the second one could very well be the fault of a bad soldering job, but from what my contractor told me, the leaks he fixed upstairs were in the middle of a section of pipe like the first picture.