I'm going to answer this from my experience with American history and do not claim to know who/what other people around the world blamed. Many of the people in the 1930s blamed Hoover, not for initially causing the Depression but because of the way that he underestimated the severity of the Depression and refused to really institute any meaningful government assistance directly to the people. Hoover did not think the government should offer direct relief to the people (he thought it would be either local government or volunteers who provided that sort of relief), but instead eventually tried to implement a trickle-down approach to help lift banks and businesses out of trouble. This approach did not sit well with the people of the United States and as the Depression maintained and didn't quickly return to a normal level they began to turn against him. His popularity with the American people in this trying time was certainly not helped because he campaigned on his role in the economic success of the 1920's and even as he recieved the Republican nomination he claimed that poverty was almost over as a result of his/the Republican party's policies. The people of the United States did not agree with him on this (after the Depression started, before hand they believed him and elected him by a margin of about 6million votes) and ridiculed/mocked him by naming obvious signs of poverty after him. E.g. An empty turned out pocket was called a "Hoover Flag" and the shanty towns that sprang up in the Depression as people lost their jobs and homes were called "Hoovervilles". Sources:

• Herbert Hoover, Unemployment, and the Public Sphere: A Conceptual History, 1919-1933 by Vincent H. Gaddis
• First Political Casualty of the Great Depression: The Tragic Presidency of Herbert Hoover by Jennifer Ostwinkle