A DigitalPoint user references the MSDN blog post from March 28th that says that the operator was taken offline because the tool was being abused:
We have been seeing broad use of these features by legitimate users but unfortunately also what appears to be mass automated usage for data mining. So for now, we have made the tough call to block all queries with these operators.
However, they add that they're "doing [their] best to get this back online as soon as possible in a manner that allows folks that use this functionality for real queries." Since it's been over a month without an update, the community is getting anxious. It was a useful tool, and I hope it comes back soon -- or at least that the MSDN blog gets updated with new information.
Forum discussion at DigitalPoint Forums.