In fact, it is still so low that it is likely not useful evidence at all. Let's say there are 50 serial killers in operation in the US. And the MeFi thread ci

In fact, it is still so low that it is likely not useful evidence at all. Let's say there are 50 serial killers in operation in the US. And the MeFi thread cited had 100,000 uniques. Even if all 50 killers read the thread you would still get a huge false positive rate if you are counting on that thread in the browser history alone telling you anything.