As indicated in earlier reports, Google is in the midst of updating their search index. This particular update is being referred to as "Bourbon". Perhaps it's named this because of the amount of potential stress that index updates can cause.

According SearchEngineRoundtable, the final segment of the Bourbon update is underway and should be completed by next week or so. As indicated by Barry's post, GoogleGuy made an appearance on the WebmasterWorld forum explaining where exactly the update stands:

...we completed a binary push this weekend that has hooks for the last part of Bourbon. We'll turn on one datacenter, and then the rest of the datacenters over the course of the next week or so. After the other changes that went out, this last change should be less noticeable.

Hopefully, this result won't cause the calamity that's been associated with past Google updates. Judging by the tone of GG's post, this apparently is the mindset of Google employees as well.