Representative democracy allows governments to expand far beyond what is reasonable. Responsibility is inversely proportional to the scale of the organization. A person that feels responsible to a dozen, or even a hundred people, will find it difficult to muster the same loyalty to several thousand. Expand that to a million, and it becomes impossible to assume the gravity of representation, let alone the responsibility of it.
Even should a public representative genuinely want to do good, it is inconceivable that any single policy should uniformly be appropriate for a population as diverse as the United States. Direct democracy doesn't work at a large scale. The logistics are impractical. By necessity, issues would be forced to a smaller, more local scale. Power, being removed from the federal government would return to the more local governments, and accountability would rise. As citizens feel the power of their franchise again, they will take it seriously and become involved in legislating their environment.
More technical arenas (such as Hulu, Reddit, Facebook) already provide the tools for direct democracy. Citizens in those communities see the value of voter participation and actively participate. The ebb and flow of information is raw power, and those who are corrupt or bad citizens get voted down very quickly.
In an age of smartphones and computers, we are living in the easiest time since the dawn of man to implement a direct democracy. I have had a long held belief that we should replace the house of representatives with a direct democracy governed by the people. Our constitution is a masterfully laid out document, with a great series of checks and balances. A president, or some figurehead will always be necessary to represent the nation. Imagine though, if the president knew that "the people, we the" within seconds of a political mishap could draft an article of impeachment. I think presidents and all the rest of those in government would take their jobs a little more seriously and start acting for the people.