The is ACORN's purpose: "ACORN, the Association of Community Organizations for Reform Now, is the nation's largest community organization of low- and moderate-income families, working together for social justice and stronger communities."
A couple of filmmakers encouraged a couple ACORN employees to act unprofessionally for the camera and then used the lapse of professional judgement to tarnish the organization. This is obviously a political smear campaign.
ACORN CEO Bertha Lewis has twenty years experience in community organization, and no doubt has done a great deal more good than her opponents. The organization has the following campaigns: Foreclosures, Gulf Coast Recovery, Immigration, Living Wage, Paid Sick Days, Voter Engagement. I think most people see the benefit of such an organization on their side, yet the smear has been successful.