The main aim of Bigdaddy is to deal with "web spam" (e.g. pages consisting of 'scraped' search engine results) and a number of cheating re-direct tricks For example, the search engines see one page; human visitors see another. BMW's German site was removed from Google's index for pulling a stunt like that! BMW sensibly removed the re-direct and they're back in. Bigdaddy could also result in many near-identical websites being removed.
It's important to understand that this is not just an algorithm change like big updates in the past. It changes the way in which the whole Google search engine works. It contains new code for sorting and examining web pages.
Matt Cutts is a Google search engineer who has become quite a public figure. He's a very useful channel of communication between Google and webmasters (I had a talk with him at a "Webmasters World" conference in London a couple of years ago - he's a very approachable guy).
Matt has a very informative blog, and he's been drip-feeding us with info about Bigdaddy on a regular basis. On 1st February, Matt posted news to his blog that Google was converting data centers at the rate of one every 10 days (Note: Google uses a network of data centers with different IP addresses to answer search queries. These decentralized servers share the workload of indexing web sites.)
There are now at least 3 data centers running Bigdaddy. There's one you can test here. Note that this may not always show Bigdaddy results because data centers are sometimes taken out of the rotation for testing purposes. One way to test it is to enter the search term "sf giants". If the first site on the results page is 'giants.mlb.com' then it's a good chance that the data center is running Bigdaddy.
You can read Matt Cutts' blog here. Check out various entries in January and February for his Bigdaddy news.
So what does Bigdaddy mean for most of us?
Possible very little, if you have a normal website and you don't try to fool the search engines. In fact, if some websites are removed from the index, others are going to move up the listings.
I was please to find that when I typed in "selling and marketing techniques" into a Bigdaddy-powered search box, my Marketing Magic website was at #1! And I couldn't find my site with this search phrase when I used one of the older data centers.
But if you have a website which is nearly identical to other people's sites, you could well have a problem. That's why, as a matter of some urgency, I am replacing the current AdSense Starter kit in my Newbies Starter Kit with a site that owners of the Kit can easily customise and make unique. I needed to find a way for people to do this easily.
(From my Marketing Magic "News Update" newsletter)