Kichwas
Half-breed
Exactly:DarkMaster said:searching doesn't set the trap, disable device does. House rule is actually needed
PHB Page 72, under Disable Device:
If you fail by 5 or more something goes wrong. If the device is a trap, you spring it.
PHB Page 81, under Search:
No such equivalent entry.
PHB Page 65 under take 20:
...if you did attempt to take 20 on a skill that caries penalties for failure (for instance, a Disable Device check to disarm a trap), your character would automatically incur those penalties before he or she could complete the task (in this case, the character would most likely set off the trap). Common "take 20" skills include Escape Artist, Open Lock, and Search.
From the above we know that you can take 20 to search, and that failing search does not set off traps - disable device does.
As to the idea that a Rogue's vision is not good enough to spot those super hidden traps - it is. That's why only rogues can spot trap DCs above 20, and even that only if they have the ranks to do it. Ranks that represent special training and a different paradigm of thought and action than others possess.
As to the effect this has on play - it only lets the rogue -find- the trap. It does not guarantee she can disable it. Just ask Lidda (as seen on page 85 of the PHB).

In fact I would wager it's more challenging when you know the trap is there. Once you know it's present you have to come up with a plan. You have to either outroll or outthink it. When you don't know all a trap represents is random wandering hit point loss.
