If you've worked on a few Drupal sites, no doubt you've run into one of those horrendously slow sites. To call it a pig, would be unfair. Pigs can actually be quite fast. (http://en.wikipedia.org/wiki/Pig_racing)
Or... How I got my server to run OK without wasting too much time.
Database performance, whether in Drupal or any other platform is serious business. There's a lot of benchmarking, analyzing queries, forming hypotheses, making changes, benchmarking again... I've done it and it can take a team weeks to hit performance targets on a major enterprise application. Everyone wants a shortcut. There really are no shortcuts, but sometimes a few tweaks can get you to "good enough".