The Weight of Software
There is a common believe about software that it is essentially weightless, that copying it is essentially free, and that it does not age. This strikes me as the kind of fact that is technically true, but of very little practical value, like proving that some system is Turing complete and stating that it can do any computation you want it to. Technically true, at least in a certain sense, but not interesting.
What I mean by this is that software has a lot of properties that physical objects have. The actual copying of software is cheap, but if you make a copy and give it to someone, they have to invest resources to use it- to compile, deploy, understand, modify, etc. It can actually be very resource intensive to "copy" the knowledge into another person.
Software also has a certain weight to it- larger software has an inertia that makes it hard to change. Large software can be hard to install, and it can be fragile in its dependencies as if it were a building with a shifting foundation. Software size is very much correlated to complexity and bugs.
For aging- software seems to bit-rot much faster than I ever expect it to. It may only work on one machine, or stop working due to dependencies or operating system updates, or any number of things. In fact, there seems to be a great deal of software that is in a constant state of decay and requires manual renewal to maintain. Sometimes it seems that the most enduring software is not Lisp or Forth, or any other of the more 'pure' languages that one might be able to implement oneself to restart computation from scratch, but rather, in practice, good ol' POSIX compliant C.
Overall software feels like a terribly complex, constantly falling apart mechanism in many cases. This is far from the ideal free to copy, unaging, machines that it is sometimes imagined to be.