Have you seen the TV ad for the latest scam from 23andme.com? It's as bad as the "blood type diet" bollocks.
Although previously banned by the USFDA, because DNA can't predict, e.g., the likelihood of heart disease, they are suggesting you can make health decisions based on DNA while the small print says "for informational purposes only", i.e., it's useless.
Talking of small print, I read a review on Amazon that says it better than I could:
"the fine print is that, even if you decide to opt-out of their research program and don't give them any "Self-Reported" information, they still sell their partners more than enough data to connect your name and location (among other things) to your genetic information. For instance, they collect your "Web Behavior Information" including your IP address, operating system, your ISP, browser type, cookies, anything you mention in your emails to customer support, and worst of all: web beacons. These are special cookies that track all of your browsing history. A cookie from Facebook can instantly give 23andMe access to your FB profile name. Any profile picture you post on 23andMe can be downloaded by an app developer. App developers are given access to your traits. How many people in a specific zip code of a small town have 1) red, curly hair 2) are good at sprinting 3) have bad teeth 4) poor memory 5) and diabetes? All of this data -- combined with your "web behavior and genetic information -- makes it incredibly easy for any app developer (or drug company) to identify you (even if the developer (technically) only has access to your "anonymous" id number). It is especially easy to identify males who have some sort of relatively uncommon disease. Overall, 23andMe's privacy FAQ is very misleading, and possibly illegal."