23 and Me logo, which mimics a chromosome illustration.

Many of us would be delighted to contribute to medical advances. But handing over reams of our genetic, health and personal information to companies like 23andMe – and paying them for the privilege – isn’t the best way to do that. And it’s far from the only path to scientific advance.

23andMe is a commercial enterprise. Its business model depends on packaging and reselling its customers’ genetic data and other information. Earlier this year, 23andMe announced the first two of a number of deals with pharmaceutical and biotech corporations, including some of the largest in those sectors.

Is that what purchasers of the company’s spit kits had in mind when they read the consent document that begins, “23andMe aims to make and support scientific discoveries and publish those discoveries in scientific journals?”

But once you part with your genetic information, there can’t be guarantees of privacy and anonymity, as 23andMe’s consent document acknowledges. And while a 2008 law prohibits health insurance companies and employers from discrimination based on genetic information, the law does not cover disability, life or long-term care...