First seen in SG1, and now a common feature in SGU. I'd like to discuss here their usage, their meaning, and whether they should be allowed or not.
Originally, we thought them to be simple devices, that put two people in a coma-like state, whilst their minds took control of another's body (Daniel and Vala in this case). Come SGU, we've come to the conclusion that minds actually swap instead. I'm not sure why there is a difference, I may have missed an explanation somewhere.
Anyway, suffice to say, when Daniel and Vala used them, they unknowingly caused the deaths of the couple in the Ori Galaxy. That has been the only real use of them since. Now we move on to SGU where these stones are seemingly used in every episode.
We've got people doing everyday things, whilst actually using another persons body. Be it fighting, drinking, having sex etc. Surely this would break some moral rules somewhere along the line? It also complicates the more dark area.
If someone was murdered or raped on the Destiny, the culprit could no doubt simply state that they weren't actually themselves, and that another had control of their body; there would be no way to prove their word.
Using the rape / murder as an example there, I've no doubt people would have others. But anyway, I know (for instance in SGU) there is a good cause for them, but is the cause justified?