Plant molecular farming is a new and promising industry involving plant biotechnology. In this review, we describe several diverse plant systems that have been developed to produce commercially useful proteins for pharmaceutical and industrial uses. The advantages and disadvantages of each system are discussed. The first plant-derived molecular farming products have reached the marketplace and other products are poised to join them during the next few years. We explain the rationale for using plants as biofactories. We also describe the products currently on the market, and those that appear likely to join them in the near future. Lastly, we discuss the issue of public acceptance of molecular farming products.