There are two very recent stories talking about how sex offender lists have been incorrectly used by the populace to exact revenge on sex offenders, sometimes with grave results.  In Los Angeles, a man was murdered by someone in his neighborhood, because he thought he was protecting his daughter from a potential child molester.  The problem is that the victim wasn't on the list because he was a child molester (via Slashdot):

Convicted rapist Michael Dodele had been free just 35 days when sheriff's deputies found him dead from stab wounds last month in his mobile home. They quickly arrested his neighbor, 29-year-old construction worker Ivan Garcia Oliver, who made "incriminating comments, essentially admitting to his attacking Dodele," police said.

Oliver pleaded not guilty to charges of first-degree murder, burglary and elder abuse on Nov. 30.

A neighbor of Oliver's said that two days before the killing, he "told every house" in the trailer park that he found Dodele's name listed on the Web site of convicted sexual offenders, and was uncomfortable living near him.
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As it turned out, Dodele was not actually a child molester. His records show he sexually assaulted adult women. But a listing on the Megan's Law Web site could have left Oliver with the impression that he had abused children because of the way that it was written.

And this is a problem that I've mentioned many times.  Many communities are passing ordinances preventing people on these lists from living in certain areas as if they were all child molesters.  But the reality is, there are many ways to end up on these lists, some of which are rather questionable.  Should an 18 year old who had sex in high school with his 17 year old girlfriend be labeled a sex offender for the rest of his life?  Should he have to be afraid of vigilante justice?

Even scarier is this case in Las Vegas (via Hit & Run):

It's worse during the holidays. Christmas, New Year's, Halloween. That's when they really start knocking. Calling him out in the middle of the night. Showing up at his stoop in angry packs.

"Christopher," they wheeze through the front door, "Christopherrrrrr - we know you're in there ... "

Christopher Risdon is a 35-year-old sex offender who was busted for child porn. But Risdon doesn't live at this Tropicana Avenue apartment. Hasn't for years. So when the curious (if that's really all they are) come calling, they're now ringing the wrong doorbell. Despite what sex offender-tracking Web sites say, this apartment belongs to Harry Berlin, 71 years old, frail and, frankly, petrified.

In this case, it's the offender's responsibility to update the database with their current information, and many times they aren't.  Now people who move into the homes of those previous occupied by sex offenders are paying the price.  And of course, with more and more communities passing Draconian laws against sex offenders, they have less and less incentive to keep their information up to date which will only make the problem worse.  As for this poor 71 year old man... he had to contact the ACLU and crawl through numerous hoops just to prove he wasn't a sex offender.  So much for innocent until proven guilty.