Just to unburden myself of something that has been bothering me, people promoting economic "mustard seeds" need to be a little more careful in their metaphors. Here in southern California mustard is an invasive species, one that was uncommon fifty years ago and is now everywhere, crowding out indigenous plants, like wild flowers.
Even more worrisome? Invasive mustard plants here in SoCal add considerably to fuel load, making the annual fire cycle much worse than it would otherwise be. Whole hillsides of the stuff sprout up in the spring and then dry out in a flash, creating a ready-to-burn landscape when the Santa Ana winds come calling in the fall.
So, to the extent that people are arguing that we are seeing new non-native species take over markets, and those species are making markets more conflagration-prone, then keep right on with the whole "mustard seed" thing.