23andMe explains it so much better than me
I haven't really made up my mind about these personal genomes companies yet. Not that I think there is anything unethical about them, it is the science I cannot make up my mind about. Technologically, it is cool that you can actually type a million tagSNPs for $1000 (with the current value of the dollar that is essentially for free), but how much can you really use the information for?
Tracking the genealogy can be done with some accuracy -- not sure exactly how much accuracy -- but the disease risk stuff I am very sceptical about. The genetic factors of life style diseases that we know about have so little relative risk that calculating it for individuals as part of some genetic profile seems a bit dodgy to me.
Knowing that a particular genetic variant increases the disease risk ever so slightly tells us about the underlying biology of the disease, and that information is important. Making medical decisions based on the type of an individual, if the relative risk is tiny fractions of the environmental risks we know about anyway, is just plain silly.
If you know that smoking increases your risk of cancer dramatically, but you don't stop smoking, are you likely to benefit from knowing that your genes increase your risk from 1% to 1.1%?