hehe, back in the day when cs was in version 1-1.3 long before steam, me and my friends would go to hastings and open a halflife box, write the cd key down then leave.
Software registration schemes aren't related to security in the traditional sense. For example, when we type in the serial number and activate Windows, this is a separate concept from security flaws in the operating system, which are patched by the Windows Update mechanism or service pack installs.