No, I don't think we can tag Hoover for this. He was President for only ten months when the stock market crash happened. He just unfortunately was the man sitting in the Oval Office when it took place. We can criticize his response to the Great Depression as tepid and ineffective, too little too late, but I don't think we can blame him for the crisis itself. There was plenty of blame to go around for that, most of it on American businesses and banks, as well as on the American consumer (sound familiar?).
I don't think so. It is almost impossible to think that any one individual started something like the Great Depression. It is possible that there are some things that Hoover could have done that might have made the depression less severe, shorter, whatever, but this is much different that saying he CAUSED it. And what did Congress, through either inactivity or poorly designed policies, contribute to the Depression.
To take a modern example, let's suppose that the steps that the Obama administration it taking to improve the economy do not work and we slide into a Depression ... would we say that he was responsible for it? The Congress? The Treasury Department?
It's immensely complicated. I think this topic needs a great deal more research. A related interesting question would be whether Roosevelt's New Deal policies ended the Depression ... it has always been assumed that they did, but there is recent research that the War ended the Depression and not FDR's policies. This is beyond the present scope of my knowledge, but I'm working on it :)
It would not be proper to attribute the Great Depression to any single person or event.
The event which cleared marked - but not really caused - start of the Great Depression is crash of New York Stock Exchange in 1929. Different people attribute different causes for triggering this crash. But no trigger would have caused the crash unless the stock prices at that time were highly inflated beyond their real worth in terms of the value of real assets they represented. Just as a highly over inflated balloon bursts with juts a touch of a needle the highly inflated prises tumbled down like an avalanche with the slightest hint of possibility that every thing may not be all right with the economy or with stock market.