With inflation running so low in the U.S. for so many years, it's easy to try to extrapolate this trend as the new norm. And, yes, there are technology pressures that push costs down (i.e machines replacing workers, Moore's law, etc.)

However, there are two big factors that argue against long term deflation:

1) Employee wages: Built into the compensation system is a review process that rewards workers for their work. To date, this process includes a wage increase in the form of a "raise". In an era of full employment, periodic raises push costs up, which leads to increases in prices, which leads to inflation. To change this, the compensation system would need to be changed or employment severely reduced.

2) Central Banks: Most central bankers will use all their tools (in the form of monetary fiscal policy) to prevent long-term deflation. So, there will likely be a major counter-acting force from large governments over time.