There's an excellent discussion of so-far-failed USDA attempts to define and regulate the term "grass-fed"; for those new to the terminology, it's important to realize that these words alone mean little. As Glenn Elzinga says, "if they want to know how the beef is actually raised, they will have to do a bit of investigating."
In the same vein, Elzinga repeatedly emphasizes the importance of keeping the business small enough to cultivate diversity and attention to detail. The corporate "grass-fed beef" that may take advantage of the trend will not be the same product:
...the implementation of the system is very unlike finishing cattle in a feedlot. For example, sometimes we move our cattle 3 times a day—other times we move them once every three days. It all depends on weather, grass quality, and the condition of the animals. Excellent grass fed beef is truly an artisanal product. Every two weeks, we handpick several head as ‘ready’ from our yearling herd, carefully evaluating each steer for the right amount of finish. The genetic diversity of our herd prevents us from categorically shipping a large number of animals off to the processor at any one time. Each animal responds to grass differently. One animal may finish in 14 months, another may take as long as 20. In the industrial model of the feedlot, it is important to strive for uniformity, both through genetics and feeding regimes, so that animals grow very rapidly and entire pens of cattle finish at the same time, often in 13 to 15 months.
What most large grass fed producers have done is put their cattle in a feedlot, feeding them a consistent forage-based ration during the last 60 days of life to eliminate the inconsistency of their products. This feedlot-finishing, however, creates many of the same problems that are associated with the current system of finishing animals in confinement on a grain-based diet. Most people interested in organics are interested in the whole picture of how their food is produced, a picture that includes humane treatment of animals, elimination of concentrations of waste that cause pollution problems, reduction of E.coli contamination, and support of small family farms.