In the old days, we had what were considered "academics". These were the people who could stand around and spout a million useless details about technology, but in the actual trenches, had no if/then/therefore logical skills. They were like autistics, in that they could memorize rote, but it often seemed as if the people who actually could excel at the times when someone had to pull raw intelligence and creativity out of a hat, they failed horribly.
The people who actually had to work in the fields often found the certifications to be far from what was required to actually master a subject - epic fail for those selling technology or selling management that certifications were actually a good gauge of mastery.
So, what started to happen was people who actually were deeply immersed in technology started to attend bootcamps which were given often during a convention, where a full immersal of the student into the subject matter's pure "academics" would occur, whereupon all the useless facts that are never used when implementing and maintaining the technology get retained just long enough to pass the certification. In this way, everyone could give a Class A subnet answer (even in the days when everyone only used Class C subnetting) for instance for a Cisco CCNA (which I obtained in 1999).
I certified in IBM High Speed Networking Technology in the 1980's at USBank, and it was a complete exercise in rote memorization. I certified on Websphere V in 2006, and nothing had really changed; little on the test actually translated to being able to manage application servers in any real world shop.
I doubt very much this has changed with regard to Virtualization quizzes - except that Linux certifications are generally excellent (especially the RHCE - which is a complete PRACTICAL test, no reference materials are allowed, and the student must master the subject on a virtual slice or real machine during the test). A RHCE is sold to businesses as a way to get a cheaper rate on their RHEL licenses. I was hired in a contract gig to build new application servers (8 Prod/Dev + 1 database all Dell 1950's 2850's) and clean up Apache security and little Linux issues while they sent their Microsoft staff to RHCE Fast Track school (Choicehotels.com):
http://www.supershareware.com/info/whizlabs-rhce--red-hat-linux-certification--exam-simulator.htmlhttp://www.scribd.com/doc/16314048/RHCE-Red-Hat-Certified-Engineer-Linux-100-Success-Secrets-on-RHCE-Linux-Test-Preparation-Study-Guides-Practice-Exams-Braindumps-Certification-Exa
https://www.redhat.com/certification/rhce/?s_kwcid=TC|3636|rhce||S|p|3282576651www.linuxlearningcentre.com/content/prepguide.pdf
The RHCE fast track (5 day type of bootcamp) is the best way to certify as well because Linux people generally don't require a 3 month class, and simply get in and do things quickly to grasp a course:
https://www.redhat.com/courses/rh300_rhce_rapid_track_course_and_rhce_exam/