From some rumors it is supposed to be this magical software that you can use to gain an instant ranking but I don't think we'll ever see something like this. You would better start doing some serious SEO (Search Engine Optimization) yourself and not hoping to find this holy grail.
So why the fuss for this? Because there are under 50,000 results on Google for GoogleTestAd thus being a very competitive keyword (the ratio between the number of searches and the number of sites that use it is very high). Unfortunately most of the results returned are link farms and crappy search engines (that search only through porn sites for a certain word).
I'm not sure if someone from the Google Labs "threw" GoogleTestAd in the game (maybe they were testing the Google AdWords program) but the certain thing is that in some days Wordtracker shows over 1000 searches for it, which is really something.
Wikipedia added a more accurate description for the GoogleTestAd phenomena (thanks Bjorn):
From Wikipedia, the free encyclopedia.
Googletestad appears to stand for Google's Test Ad which is used for live testing of their AdWords and AdSense pay-per-click (PPC) advertising system.
At the moment there are no define: googletestad definitions in Google's database for this keyword.
The Google Test Ad
The following paid advertisement appears for a Google search on googletestad:
Popularity of googletestad as a Search Term
In June 2005, googletestad began appearing increasingly in the top search terms for search engines such as Overture_Services,_Inc.. and WordTracker.
In July 2005 this keyword was consistently in the top 30 searches as measured by WordTracker, and received over 100,000 searches according to Overture_Services,_Inc. thus:
72,161 searches - google googletestad monitor query
39,436 searches - googletestad
96 searches - foo google googletestad monitor query
The WordTracker Keywords Report dated August 9, 2005 (top 10 queries from the last 48 hours) reported:
1 jessica simpson (3377)
2 jessica alba (3314)
3 music lyrics (2679)
4 daniela hantuchova (1955)
5 paris hilton (1469)
6 playstation 2 cheats (1243)
7 xbox cheats (1231)
8 jokes (1069)
9 googletestad (1048)
10 google (1013)
Regarding the keyword's trend, back issues of that service's Top 200 long-term keyword report (for the last 110 days) showed gaining popularity:
(date - rank, and count)
August 9, 2005 - 55 (35,032)
August 2, 2005 - 64 (32,737)
July 26, 2005 - 94 (28,793)
July 19, 2005 - 105 (24,878)
As of August 13th 2005, there were 12,800 hits found for googletestad in Google's search engine.