I don't know about Ancestry.com's current effort, but getting my DNA done did cut a Gordian knot I'd encountered in my own research. Every indicator (except documentary evidence) had pointed to an African branch being grafted onto my otherwise WASP-y tree somewhere along the line; it took a cheek swab to confirm that my maternal grandfather was 1/8th Black. I was jumping-up-and-down delighted to get this news, not that my grandfather probably would have been happy to be "outed". But, unlike me, he lived in the Jim Crow era and it's doubtful he would have gotten as far as he did at AT&T, let alone been admitted to Dartmouth (Phi Beta Kappa, class of 1908) if his heritage had been generally known. Getting dramatic results like this isn't uncommon in genetic testing. I think knocking the whole concept without knowing what kind of impact it can have on individuals is another example of the anti-science bias of Bush-era America and not really worthy of Newsweek.

Oversold?  I've been doing DNA Testing for genealogy now for over 5 years, and I have found a "lost" son from one lineage, confirmed a daughter as belonging to that lineage, moved that lineage back at least one generation by combining my paper trail with both Y-DNA and mtDNA, proven myself a cousin of a nice man I met in a Georgia library.  I have tested cousins, brothers, aunts, myself and my mother.  I have all my grandparents, almost all my greatgrandparents, well over half my great-grandparents and a good chunk of the DNA through my greatgreatgreatgreatgrandparents.  And yes, I've done the paperwork, so come on, because I'll share it with anyone related to me.  

As to the scientists scorning us, it might be because a number of genealogy DNA enthusiasts have advanced the structure of the DNA tree beyond them in some cases.  We don't have to write grants or wait to publish.  We plunk down our money and get our results and go to work figuring out what they mean.  We register our whole genome sequences with GenBank where scientists can access the data without having to pay one red penny for it.  So bring on the scientists who want to study the data we are shoveling their way!  

Some folks do have unreasonable expectations. On the other hand, the more we learn the more the reality is catching up with some of those expectations.  If I were starting genealogy anew, I would start by buying DNA tests for every family line I can find a living person with the right DNA for, and then I would start looking for matches and exchanging paper trail information.  With cousins spread across the nation (and beyond) it's much easier to find the documents than it used to be,  And with all of us double-checking each other, it's easier to correct those mistakes so many made in the past because everybody on the trees had the same first names.

It's an exciting time to be a genealogist, but yes, do find out what is known before you leap.  I don't think any company "oversells."   There will be some surprises, and some people may wait a long time before they get the payoff they were looking for -- but that is true of any activity.  Look at the weight loss industry!