For Fathers' Day, a buddy of mine received from his adult children a free genealogy search, which required a DNA test. (Read on, please.)

Oh my. So many questions. O_o I'm summarizing instead. 

My mom once researched family trees for both my dad's side and her side and we can go back several generations. However, my mom's research uncovered that my paternal grandfather started a family before WWII and that his brother took his place when he left to fight. Ergo, further attempts to uncover said family history were thwarted with hostility. My maternal grandmother's father was also apparently a deadbeat who bailed. My mom found out a few details and, for a while, believed he was a Spaniard based on his last name. However, she later discovered photos with names on the back. He had dropped the ending his last name; the original ended with "ov" or "off," making it Slavic, not Spanish. So, for a few years, I believed I was possibly Spanish. My father's side did that as well. My Irish ancestors placed an "O'" before my maiden name, but my family dropped it when moving to the States. 

My son asked for a 23 and Me kit for Christmas. This was a particularly difficult decision because he was born as the result of a rape. On the one hand, it would have been cool to see what his background really was. On the other, I was a bit worried it would link him up with members of his biological father's family- or perhaps even that man. I know that man fathered several other children. I'm aware of at least four others, none of whom ever had any contact with him. One mother was married to him and had his parental rights terminated. Another mother fled to Mexico when she got pregnant. And, another fled to China when the baby was a newborn. So, in a sense, my son linking up with any of his siblings probably would have been cool. He might have gained some kind of sense of belonging or found positive commonalities with the non-rapists and perhaps that would have made him feel a bit better about his origins. (Side note, my son takes it in stride anyway. He has no interest in meeting the guy because of his background, but like anyone, he's curious about where he comes from.)

Anyway, he did not meet any immediate relatives. Lots of distant cousins. I, unfortunately, could not tell which side most of them came from. He was able to see the path his ancestors took to get to America- 23 and Me will show you both your mother's and your father's family migration path. My son learned he had a fair amount of Neanderthal DNA- more than most, as well as a tiny amount of African. The rest was not surprising. I did like the "traits" section, where it talked about what traits he was likely to possess based on his DNA. It nailed it. 

I plan to do 23 and Me at some point in the future. With our luck, we will find out we are relatives after all. lol 

As far as situations where it might not be a good idea, I think, if you want to know, it's always a good idea. My son's situation was a bit extreme, and I suspect yours will be a similar journey. But, I will say this... Just because you know doesn't mean you have to act on it. You don't have to communicate with relatives you didn't know you had. You don't have to talk to people who might be painful to speak with. Knowing they're out there doesn't change anything. It does, however, give you options if you wish to pursue them. And, it is pretty cool to learn where your family comes from and find out what traits you might have or what conditions you're at risk for. 

A) yes

C) I had grandparents on both sides of my family with an interest in genealogy and have done some wiki-tree stuff. 
    I am planning on doing one of the DNA kits sometime (Trying to get a sibling to split the cost with me. I'd be thrilled to receive a gift kit!
    I'm not worried about giving up my DNA.)

D) I don't remember. At least one branch is pre-Revolutionary War. 

E) I don't see why any adult shouldn't know their family history.  

For what it's worth, I understand why Walt jumped to that conclusion about your friend. Regardless of his race/ethnicity, it sounds like he was disappointed to find out he's less homogeneous than he though. Maybe racist isn't the right word for it? Ethnic elitist? I don't know... 

My sister did an extensive family tree and I also did the DNA test when they first came out (and were perhaps less comprehensive than they are now). My test results and the family tree matched up - no surprises.  I am 99.9% European, mostly the British Isles and Southern Europe.

A. I have, and am still doing so sporadically when I can find the time and resources.
C. Other methods. DNA testing will tell me little I do not already know.
C1. My Heritage, various Family bibles still extant and cross referencing with extended family - both grandfathers became interested late in life and the information they were able to gather was passed on to my father's elder brother and my mother's sister.
D. There have been more than a few dead ends - no background information is available on my aboriginal ancestress, no written records were kept - native languages were illiterate until relatively recently, Australia's native population never developed writing. One ancestor called himself "John Smith", 'nuff said. I've been able to go back to the Spanish Inquisition with one branch. I didn't expect that.
E. If you're interested, do it. If you're not, don't. 

I have to add something. Using DNA and Ancestry, my baby sister was able to find a cousin none of us knew about and found us after 56 years. 

But why was it your friend was disappointed?  After all he is still himself.  That is what I am curious about.  Did he think that some how the race or ethnicity of his ancestors was somehow "not cool"?  Let's face it - some people do think that some races or ethnicities are more fun or desirable then others.  Thus Mr. O Reagan's "racism" question. Which would not necessarily be racism at all but many people would perceive such favoritism as a form of racism. 

I'm not really terribly interested in where my ancestors came from though I know Poland, France, England, Ireland. some by way of the U.S deep south.  I know some were extremely successful, others rednecky, some slaveholders, some slaves or indentured servants. Which to me is neither here nor there as I don't define myself by my ancestors. 

But the point is - we can't always be as cool as we want to be.  Whatever we think that is. 
!