There are two different labeling needs being discussed in this thread. My personal opinion is:
If you're running network drops and terminating them from a patch panel to wall jacks, then writing a number on the cable with a sharpie can be more than sufficient. This numbering is temporary, and will be replaced with some type of permanent numbering convention when the cables are terminated (032, 1B-04, 1A-124, 2D-001, etc...whatever applies to the environment). I think it would be rediculous for someone running structured cabling to print out labels and attache them on each end.
However, if you're trying to identify what is connected to what inside of a rack, then labeling the cables with some type of label tape is a much better solution. As an example, I label patch cables for infrastructure equipment (servers, SANs, other switches, etc) at the end connected to the switch with the device's name. I also label power cables where they connect to PDUs or UPSs with the name of the device that it is connected to. For me, the optimal solution is to trace every cable when I need to find it, but the labels are reassurance that i've got the right one when tracing it is less than optimal (i.e. in the middle of a large bunch of cables).
No one was right or wrong in their recommendation...it just depends on the type of solution you're looking for.