You want to be sure to get the most recent version of the package (the binary version will never be more recent than the source-code version and can be significantly older or completely unavailable!);
You want to support product-queues larger than 2 gigabytes;
The pathname of your perl 5 utility is not /opt/bin/perl;
You wish to modify the LDM programs;
You wish to write your own LDM-compatible programs;
You need to port the LDM to a non-supported platform;
You are using a non-standard installation setup;
You want to look at the code;
You want to fully understand an error message; or
You just like building from source.
Building the LDM package from source should add only a few minutes to the total installation time.