So said this site in August:

I've spent the past two months immersed in data from the 2008 Democratic caucuses. After studying the procedures and results from all fourteen caucus states, interviewing dozens of witnesses, and reviewing hundreds of personal stories, my conclusion is that the Obama campaign willfully and intentionally defrauded the American public by systematically undermining the caucus process.

There's a 98 page PDF at the link with her findings, and for a summary see this article. Needless to say, ACORN is involved.