I think requiring you to be physically present and having a human take the sample in a prescribed manner serves as an effective 'password' - unless it's a live sample, the DNA is useless.
I think there's a misunderstanding of what is possible with DNA[0]. We take DNA from dead stuff all the time.
I will agree with "you have to be physically present" is good enough password. This is Yubikey, which works fantastic. The problem with DNA is when it is compromised - you can't throw it away/change it without exorbant effort (bone marrow transplant? and then you're simply taking on someone else's identity? is that identity theft?).
I think people are misunderstanding what is being suggested here. The idea is that, for example, to unlock your bank account, you have to go to the bank where trusted bank employees will extract your DNA and have it sequenced, resulting in you being given access again. Others cannot spoof being you in this scenario because they cannot implant your DNA in themselves.
