I paid too much
Either there’s a bandit in town going around town and “fixing” the Apple ads on all bus stops, or this is the work of a person who was just really bored while waiting for the bus. We don’t know about you, but when we wait for the bus, we like to talk on the phone, listen to music or play something on our smartphones (after all, that’s what they’re good for).
This person must have been very bothered by this ad for iPad, since he recently received his and was evidently very disappointed (I don’t know that they market it as anything that it isn’t); and so he decided to execute his own little protest of iPads – if he saves even one person from buying it, his job is done.