Cue Keep on the Shadowfell. Kobold ambush. Third paragraph:
Have the players place their miniatures on the road near the western edge of the map. Allow each character to make a DC 25 Perception check.
Argh! What the hell? This is the very definition of a passive check. The PC's are strolling down the road. Sure, they might be alert, as usual (they're adventurers after all, and paranoid about their loot being nicked), but they're not actively searching every boulder, shadow, bush and twig along the way in case there's a kobold waiting to put the kaibosh on them. Why, Wizards? Why is there an active roll here?
Compare the [Stealth] check result against the passive Perception checks of the creatures that might notice the hiding group, or the active checks from alert creatures
Oh for heaven's sake. What is 'alert'? Are adventurers alert if they're travelling along a road? How about in a dungeon? A city street? Why even allow the option? Isn't the point of passive checks to cut down on tedious die-rolling? The game appears to have just allowed meticulous players an out, returning us right back to chez-3rd-Edition.