Summary and Info:

I have occasionally experienced that files from an upgraded package are missing from the filesystem.
Last time I ran into this problem, the files from the following packages was missing:

libsystemd
libutil-linux

which led to the my system failing to boot. I upgraded three x64 systems at roughly the same time, but only two of them had the issue. Re-installing the packages with missing files solves the problem.

To counter this, I now run this command after each update:
pacman -Ql | while read line; do [ -e "${line#*\ }" ] || echo ${line}; done

to ensure that no system libraries is missing. The above command currently finds some broken symlinks and missing license files on all of my x64 systems.

Steps to Reproduce:
I have run into this problem a couple of times, but have not been able to reproduce it after occurrence.
I guess reproducing it would require a snapshot of the system before upgrading (pacman -Suy), which I do not have the capacity for.

Suggestion:
Would it be possible to include the functionality from the command above, when running "pacman -Suy"? or is there a simple way of defining custom scripts to run after a system update?