Eventually this data will get into the hands of governments and others. Who is to say that in the future you are not permitted to own a firearm (just an example ) because you have some gene that may increase your tendancy for violence (some future research show)? What about an insurance denying you becuase of a gene? That may be illegal but it's you against Goliath. How many laws are broken by banks etc. without recourse because the ones affected don't have the resources to fight it?
Sure these are extremes but if this information is available, eventually it will be used and most likely first for for profit.
Government is 1 of the largest buyers of marketing data as well. They cant do the spying legally but nothing stops them from purchasing what corporations do.
Sure these are extremes but if this information is available, eventually it will be used and most likely first for for profit.