There's no effective method in place to enforce voting laws. It's like turning your back on a herd of elephants in Manhattan and claiming there's nothing unusual because you can't see it.
There is little or no coordination among states to detect duplicate voting. This guy would have never been caught if he hadn't boasted about it on Facebook.
I think the real voting fraud is committed by poll workers, who churn out votes for their candidates after polls close and they know who didn't show up to vote. I fear that even voter ID won't stop them, unless we can somehow confirm an ID was actually shown.
I don’t know of any other states like MN that let you “vouch” for up to 13 people just base on you saying, “Oh yeah, I know them-they live around here.”