“We don’t just get MRIs on everybody who comes to the doctor’s office. Not only would that be ridiculously expensive and uninformative,” says Evans, “it could also lead to all kinds of false positives that would be highly problematic for those people.”

And sequencing could easily end up stumbling across some terrifying things.

“There are also people walking around out there who carry mutations that create an extraordinarily high probability that they will develop a horrendous, untreatable, unpreventable disease by age 50, 60 years old,” he says. “That isn’t necessarily information that everybody wants.”

It’s not just that this might scare people — it could cause really serious, concrete problems in their lives. Getting sequenced could subject people to genetic discrimination for things like life and disability insurance.

There are even more futuristic concerns.