… or harder when you succeed?

Positive feedback: The game becomes harder when you play worse, easier when you play better.

Negative feedback: The game becomes easier when you play worse, harder when you play better.

Examples:

• Mario Kart SNES has positive feedback: Gaining a lead separates you from the fray, reducing the threat of attacks, which makes it easier to increase your lead.
• Mario Kart Wii has negative feedback: Gaining the lead means contending with more attacks designed specifically to target the leader, while falling behind means better random items.

A goal in both cases is to create a suspenseful struggle, and to this end positive feedback wins. The reason for negative feedback is that the person falling behind or running ahead is no longer in the struggle. They need some help or harm to push them back in. But that push counteracts their accomplishment or lack thereof. Their actions become less important, and so the suspense is diminished. Too much chaos, not enough control.

IGN’s Matt Casamassina said it well:

…the manner in which you advance through the higher difficulty single-player courses — a good deal of skill, but just as much luck. You can be zipping through a 150cc stage without a single error and well ahead of every other competitor when, seemingly out of nowhere, bam! Blue shell. Lightning bolt. One cheesy last-ditch effort after another by unfair AI-controlled components. And suddenly you’ve gone from first place to eighth by no fault of your own. You don’t even have a defense against these items — that is, unless you consider praying that your cheap AI competitors don’t decide to rob you of a victory.