I suspect that we are all assuming that our results are going to reflect where our ancestors were living in a relatively recent time period, when that may not actually be the case from the testing company's perspective. On the one hand, if out earliest ancestors originates in Africa, we should all display results from Africa, but we don't. On the other hand I see a lot of people complaining that their results show areas other than the British Isles when they claim that they are certain that all of their ancestors came from England without considering where the people in England came from.
My own percentages are shown as 77% British Isles and 23% Central European. FTDNA shows me as being something like 95% British Isles and 5% Middle Eastern. I recently recieved my results from National Geographic's Geno 2.0 project and the results were 43% Northern European (reference populations were British and German), 37% Mediterranean, and 19% SW Asian.
Looking at these Geno 2.0 results I would have assumed that the British Isles portion represented my more recent ancestors since presumably those folks might have come first from SW Asia and then moved into the Mediterranean region before England, yet after reading the Geno 2.0 explanation I discovered that I was reading the results in exactly the reverse order.
They said that the Northern European component likely reflected the earliest settlers in Europe, the hunter gatherers, who arrived there more than 35,000 years ago. The Mediterranean and SW Asian percentages arrived later, with the spread of agriculture from the Fertile Crescent in the Middle East, over the past 10,000 years. Today's Northern European populations retain their links to both the earliest Europeans and these later migrants from the Middle East.
I suspect that we are expecting too much specificity from Ancestry.com in their iinterpretations and conclusions drawn from our autosomal data. We are expecting there to be some sort of cut-off date in the past as when they say that the data can only show a cousin relationship back so many generations with any degree of confidence. Many people are complaining of results showing Scandinavian results when they claim to have no such ancestry. I know of no such ancestry in my own tree, although my own knowledge of my ancestors only goes back to the 1600s in most cases; yet after undergoing MtDNA/FGS testing which shows one's direct maternal lline going back for many, many, many years I have matches with people whose families have never left Scandinavia to this day. Should I complain that my autosomal ethnic pie chart only shows British Isles/Central European but no Scandinavian?
It appears that people are simply expecting too much specificity in their results. I would have to blame the company in large part for this due to manner in which they have led their customers to expect a high degree of specificity in the first place.