In recent decades, the traditional role of hobos as itinerant workers has fallen off, largely because of increasing prosperity. Most itinerant workers in modern times have automobiles and drive between jobs, alternatively they may use public transportation, and live in many types of temporary housing.
Increasingly, as seasonal agricultural work became the province of illegal immigrants, and other seasonal work became increasingly lucrative, freighthopping became mainly used by the homeless population, by thrill seekers, youths who have adopted the lifestyle as an expression of rebellion against society, and people who enjoy traveling across the countryside under the open air.
In recent years there has been an increase in crime targeted at the rail-riding homeless population and other freighthoppers by other itinerants. Retired Spokane police officer Bob Grandinetti attributes this largely to the rise of an itinerant group calling themselves the 'FTRA' or Freight Train Riders of America. Whether the FTRA is as violent as claimed by Grandinetti is in some dispute. Other increases in crime targeted at freighthoppers can be attributed to the general increase in violence and urban gang activity around train yards in such locations as Los Angeles.
Another reason the practice is declining is because the nature of the way goods are being transported, with the traditional boxcar giving way to more secure plug door cars, and eventually shipping containers, which are not friendly to people riding.
Even flatcars are becoming increasingly open, making life harder for Freighthoppers.
Also, the close and decline of much of the rail network has made the practice less common.
The Freight Train Riders of America (FTRA) is an American gang of homeless men who move about in railroad cars, particularly in the northwestern United States.
The FTRA was founded by homeless veterans of the Vietnam War in a Montana bar in the 1980s.
****Update**** This question is one I've been asking myself for sometime. It's been kind of a fantasy of mine, to ride the rails for a few weeks, just to see where I end up. This is the reason I took a little time to research the subject. My answer was obviously taken from Wikipedia, but I am so thrilled to see the answers that followed, people that have the knowledge first hand. At this time, it doesn't seem to practical or safe to hitch a ride on the rails .... but I can still dream!