Oh, yer right, I forgot my standard disclosure:
I take it, then, that you left the pits in your apricots, to no ill effect?
I will note that the kernels of all members of the rose family, including apricots, contain cyanogenic glycosides which on ingestion release hydrogen cyanide. The amounts of these chemicals vary from plant to plant and species to species. Bitter almonds generally contain the most, and eating 50-70 raw bitter almonds in one sitting is enough to be fatal for an adult human. Fortunately, in most people, these chemicals are rapidly broken down by the liver, and do not build up over time, so small doses are generally regarded as safe.
If this makes you uncomfortable, by all means, pit your peaches, plums, apricots, pluots, etc.
Though, you usually only use 6-8 plums or apricots per liter of alcohol, so you would probably reach the fatal dose for alcohol (or a diabetic coma) well before you reached the one for cyanide.
The year before last, I chickened out and pitted my plums, pluots, and apricots before making liqueur. I also had not yet read jackal10's method, so didn't freeze. I was pretty unimpressed with the liqueurs I made. Especially the plum.
This year, however, I both froze and left the pits in. The liqueurs were an order of magnitude more complex, and the fruit much better expressed.
I've noticed no ill effects from consumption.