Voter Registration Fraud and Voting Fraud? [Updated]

The Reps are pushing stories that ACORN has indulged in vote fraud (google "Acorn vote fraud". Some seem to be well-founded, at least those where indictments have been filed. I'd note a difference between "voter registration" fraud and "voting fraud" and make a couple comments, though:

• I'm assuming ACORN pays people to register voters. So they have an "agency" problem--if their agent gets paid on the basis of names and addresses of new voters, there's an obvious temptation to sign up people who are already registered, are ineligible, or whatever. So fraud is relatively easy. (It's a familiar problem--how do you evaluate performance?) To avoid this fraud, we need to open the voter lists so ACORN or whoever can match supposed new voters against existing voters and ineligible people and only pay agents based on valid new adds.
• The "fraud" of fraudulent registration is relatively harmless in itself. It simply means the voter turnout percentages appear lower than they should be. Granted it could enable "vote fraud", but I haven't noticed stories to that effect.
  
• The serious fraud would be either multiple voting by a single person or voting in a district where they aren't supposed to. I would propose a simple remedy for multiple voting: as in Iraq, stain people's fingers when they vote.

IMHO making voter lists transparent and using finger stains would mean the parties and the people could focus on the issues, and the prosecutors could devote time to other crimes.

[Updated to make my point more clearly.] [Updated again to add a link to TPM's discussion--spun, yes, but the basic point is the same.]