Comments on another question pointed out that many medical journals require "written consent of any cited individual(s) noted in acknowledgments or personal communications".
I find this requirement exceedingly strange. In my own field (theoretical computer science), acknowledgements and citations of personal communications are just another form of citation. Just as ideas/results/techniques/data from another publication require citation, ideas/results/techniques/data from another human being require some form of acknowledgement. Otherwise, in both cases, the author is dishonestly claiming credit for someone else's work. An acknowledgement gives the person being thanked no more responsibility or credit for the work than a citation to one of their papers. A citation to "personal communication" is even more clearly equivalent to a paper citation.
Clearly attitudes toward citation and acknowledgement are different in medicine, and possibly in other fields; I'd like to understand why. Does being acknowledged by a medical paper imply some responsibility toward or endorsement of the content of the paper? Does acknowledging someone famous increase a medical paper's chances of being accepted or cited? Why don't the same issues attach to paper citations?