[iamben]

I suppose I'd be more interested if you could buy the kit from a supermarket, and each kit had a unique code and password you could enter online to check for your results. So once the sample is posted, the only thing that connects it to me (without a probably unfeasible amount of detective work) would be my IP address. (And my DNA, obviously...)

[bjackman]

Hmm... that would come off as pretty suspicious; it would make it very easy to get away with DNA testing other people against their will.

[georgyo]

The 23andme kit requires a substantial amount of spit, so it would be hard to trick someone into giving you their DNA.

In terms of doing DNA testing behind someone's back, paternity testing is DNA testing, and only requires a sample of the DNA. You can buy those kits at walmart already. Search for Identigene DNA Paternity Test Kit.

[tobylane]

This kit lets you collect material by yourself. Some other kits/companies require a doctor/nurse signature that they did take material from someone who matched a photo id.