I highly doubt all celebs have been through that process, I don't think that would even be necessary for them. Another issue is, it doesn't actually work on everyone, I mean it has to be done to a child, for one. But it must require a certain kind of mind to build & maintain the separate personalities, or to disassociate as a protective measure. A catatonic or insane state is quite a common reaction to intense trauma. I'm pretty sure that "MK Ultra" was all about exploring the limitations of that trauma-golem ritual in a scientific environment, to find out what genetic or environmental variables may impact or improve the 'process,' and whether that shit could be applied to a larger scale.