Depends. If they're using that information to try to sell you something then it's only valueable as far as you're likely to buy what they've got, and even then only more valueable as far as they'll be able to make a profit. If they're using your genetic data to try to alter your genome, it's only really of use if a family member hasn't already provided theirs. It all depends on the use, but it's hard to imagine a scenario where someone's information becomes more valueable the more secretive they've become.