and will probably spur a lot of economic activity. Going from $60 to $30 provides less relief - oil is already pretty cheap at $60, there's probably not as much activity that will start up because of a drop to $30, but there will be cuts in the energy industry, both traditional (obviously) and renewable (with gas at $2/GA, who cares about electric cars). Does that 'less relief' outweigh the costs of the lower oil price? Right now, aside from the oil companies obviously hurting, their suppliers are as well - the oil industry has been a major customer for manufacturing lately - that's already started to dry up, especially for steel producers (http://www.forbes.com/sites/greatspeculations/2015/01/09/u-s-steel-idles-two-tubular-products-facilities-as-low-oil-prices-take-their-toll/)

It probably would have been more accurate for me to say that a stable, predictable price for oil is best for the economy, but even if the price is stable and predictable at too low or too high of a price it would either shrink the energy sector in the US (and impact all of the energy sector's customers) or would impact any sector that requires oil/gas/byproduct as an input.