The 5 Worst Things to Learn from a DNA Test
chromosomechronicles.com
chromosomechronicles.com
Mistaken paternity? That would be pretty lifechanging. But how exactly would a 23andMe style test let you know if you father "wasn't your father?" I suppose he would need to submit DNA as well? (Obviously if your true father is from Asia or Africa but you always thought he was European, you could easily discover this with principal components... but I'm sure that's not what this blog post's author is talking about.)
In my opinion, there is little to be gained, currently, from commercial genetic testing. Groups like 23andMe egregiously oversell their offerings: https://www.23andme.com/store/ "Learn your genetic risk for type 2 diabetes, Parkinson's disease, and other conditions." Please - at present day, your genetic profile tells you no more about your risk for T2D than does your family history.
I agree completely, the disease predispositions in the 23andMe service fall far from being of any value. http://Navigenics.com and http://www.deCODEme.com do a better job at this.
How about significant genetic overlap with your significant other? Or you carry hereditary diseases that you'll pass on to your children? Or that your DNA is partially composed of frog's DNA? (Why do you think those dinosaurs were so angry?)
Accidental inbreeding would be horrible.