Check out CNN.com's article about "daylighting" - a practice of having two careers at once. In the same shift, with the employer either knowing about it OR not knowing about it.
I'd guess increasingly offices have many variations on this theme ... eBay "career people" ... those who spend vast amounts of time during a workday "building their [other] business" using social media ... or just a full-fledged second job, simultaneously. The reason (obvious): Income.
Word of the day: Daylighting