Does anyone know of any examples of 'dishonest' pheromones, and how these could evolve?

I think you will find that they are called allomones, or synomones if they benefit both parties.

 

A classic example is in the bee orchid, which produces insect pheromones to attract bees to aid in pollination.

 

Though my favourite would be the Arums, which smell like rotten meat to attract flies to pollinate them. I had one in the house once and when it flowered I promptly got told, by the wife, to take it outside.

 

Their evolution should be quite easy to explain, as many plants are pollinated by insects, obviously ones that are better adapted to attract insects will thrive and evolve through natural selection. Even if it means smelling like rotten meat:D