Overall, deregulation was a problem. Corporations could form giant trusts and thus create monopolies. This led to a lack of competition in some sectors, such as oil and steel, and allowed corporate leaders to charge whatever they wished. Deregulation also extended into retail goods, as patent medicines and unsafe food killed thousands each year. The United States had a large unskilled labor pool and the worker was treated as expendable and compensated accordingly. Government refused to get involved in business, and it allowed business to make their own decisions; this led to a focus on profits, and it minimized both the consumer and the worker.

Another problem partially stems from the social tensions caused by the competitive labor pool; the United States went through a period of extreme xenophobia during the Gilded Age. Immigration surged during the period and native-born workers did not appreciate the competition for their jobs. Workers in the North also did not appreciate the northern migration of poor whites and blacks, who were trying to escape the South's postwar poverty. In California, Chinese immigrants were accused of stealing gold claims when, in reality, they only mined them more closely than the previous owners who had abandoned them once the easily found gold was removed. These ethnic tensions led to lynchings in the South, riots in the North, and even a bill excluding poor Chinese from coming to the United States, which was one of the first attempts by the United States to limit its immigration.

In addition to the problems mentioned above, I would add that the Gilded Age witnessed massive and rapid urbanization that led to deplorable living conditions in many urban areas. To use New York as an example, the Lower East Side became filled with immigrants, both from abroad and from the countryside, and many were crowded into inexpensive tenements. These buildings, filled to many times their capacities, became dens of disease. Working-class neighborhoods degenerated into slums, where people suffered from unsanitary conditions, massive crime, and general lack of economic opportunity. These conditions were all the more deplorable for the fact that they occurred, as Jacob Riis famously pointed out in his expose How the Other Half Lives, a few blocks from some of the richest neighborhoods in the United States.

There were a lot of problems that arose during the Gilded Age.  Let us look at three of them here.

1. Corruption in government.  This was a time in which big businesses came to dominate the economy.  They also came to have a tremendous influence on government.  They were able to essentially “buy” people in government who would do their will. 
2. Problems for workers.  This was also a time of cutthroat competition between companies followed by domination by trusts and monopolies.  Both of these were bad for workers.  They led to situations where workers worked in dangerous conditions for long hours and got low pay.  All of these things helped lead to a rise in union activity and labor strife.
3. Problems for farmers.  The railroads became absolutely necessary to farm life.  So did banks.  Both had a hold on farmers and used that hold to exploit them to some degree.  Banks imposed onerous terms on loans the farmers needed.  Railroads charged high prices.  These abuses helped lead to the rise of populist protest and other political activities by the populists.