Stickers, paint, ink and so on can also disguise evidence of potential warranty-voiding activities, such as deep scratches or dents from a large drop, or a scar left from a burn -- who sets a soldering iron on an XBox360, anyway? -- or other similar. In a place that handles warranty repairs, thoroughly checking for warranty-voiding causes of malfunction seems good business practice.

Microsoft here, as in most areas, was overzealous.