[slonomo]

Toe out on a single a arm suspension will cause the front suspension to "squat" while moving forward on pavement. If the wheels are pointed outward the cart will want to steer left then right and repeat. That's what leads to "squirrely handling".

Why you say? The natural thing for the tire to do is to travel in a straight line. When pointed outward, the two tires want to move away from each other. This causes the tires to put upward pressure on the a arms, which causes the shocks to compress. The result is front end squat.

On a single a arm (aka swingarm) front suspension, the tires must be toed in slightly to avoid the bad steering and suspension squat. The toe in setting allows the suspension to do the opposite action, which is lift itself, in forward motion.