Version 1.6 has an accuracy of 81.9%, meaning that for every hyperlink it inserts, there's a roughly 1 in 5 chance that the link won't lead to the cited source. This error rate was unacceptable (to me, and probably to you as well), which is why I've been working on some major tweaks.
Version 1.9 is much more accurate -- it has a success rate of around 92%. It achieves this by ignoring a host of citations to sources (mainly regional reporters in the U.S.) that it knows can't be found.
Ninety-two percent still leaves room for improvement, but at least it's within the bounds of respectability.