When using {NoAI:1} modifier when summoning pigs with saddles, the pigs gain AI when you sit on them and hold a carrot on a stick. They lose their AI again when you dismount the pig.
If you summon a Horse with {NoAI:1} they the gain gravity, but not complete AI when you mount them.
If you use the entitydata command with the {NoAI:1} modifier on a tamed horse it gain it's AI when you ride it, then loses it again when you dismount
NoAI=WAI.