Frequent flyer miles (and hotel points) are a massive perk for traveling employees. Most consultants I know finance annual vacations completely on points. Every once in a while, a big company will try to pocket the points for themselves, usually to great outcry--because it's akin to cutting benefits.

The corporate thinking is: "Points are a reward for buying travel. And I'm the one footing the bill." The employee thinking is: "Points are a reward for traveling. And I'm the one on the damn plane."

Personal perks on a corporate card are similar, and again, do the math of how many points you get by channeling $60-100k/yr worth of corporate travel expenses through a credit card.