Shaddows - 8:04 am on Jun 8, 2012 (gmt 0)
Embarrasing. Emphasise a sentance with a typo.
"profiled by niche". Not "nice". A Moderater change would be appreciated.
By way of expansion,
"It is used for LOW VOLUME sites... or sections of sites where that site has been differentially profiled by niche"
So, we span a few niches. In the real world, its a single, integrated business. But online, it really isn't. Take @diberry's example of Employment Advice.
Dressing For Work lives in the ultra-competitive fashion niche. Contrary to diberry's example, lets assume it performs extremely well, dominating the volume searches, all due to excellent content and WH SEO. <Business Suits>, <[Brand] Suits>, <workplace fashion>. That type of thing. Big corporate players in this space, but still being outranked.
Then there is the semi-pro areas, where a load of large and mid-size players compete. Employee rights, getting a job, interview techniques. Loads of trash sites mixed in here. Totally different market from Goog's POV.
Then there's the low volume areas. Keeping a job, getting along with colleagues. Different market again.
Now, you might be rock solid in the competitive Fashion niche, but you're site as a whole is about Employment. Maybe you haven't put as much SEO into "Keeping a Job" although you rank well due to good content, not much (worthy) competition, and sitewide factors.
G thinks "This niche is not very competitive, better establish some qualitative data" and starts running some testing. Some sitewide factors get re-evaluated, impacting parts of the site that weren't tested.
Sites without the breadth wouldn't have their solid traffic in the non-tested areas to rely on. This doesn't explain what happens to their "normal" traffic though, unless its Traffic Shaped away from users that aren't the Test dataset.