As we constantly leave bits of our DNA around the environment, I wonder if it would be worthwhile for an unscrupulous company to just collect DNA for nefarious

As we constantly leave bits of our DNA around the environment, I wonder if it would be worthwhile for an unscrupulous company to just collect DNA for nefarious purposes. I'd guess that they'd need the DNA linked to a person for it to be worthwhile, so maybe an easy collection device would be to send out a return addresses envelope for entering a prize draw or something, and then collect the saliva used to seal the envelope (i.e. not a self-sealing one, but one that you have to wet/lick).