What does being acknowledged in a medical journal imply? 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?
From the Lancet:


  Acknowledgments — written consent of cited individual


From CMJA:


  Authors should specify, in the acknowledgements section, contributions to the paper that should be recognized but do not justify authorship, for example critical review of the study proposal or assistance with statistical analysis. The Canadian Medical Association Journal (CMAJ) requires that these people give their written permission for their names to appear in print.


From Infection Control and Hospital Epidemiology:


  Thank you notes. Persons should not be thanked in the Acknowledgments
  section without their knowledge and consent. Authors will be asked
  during the submission process to confirm they obtained permission from
  all persons thanked by name in the Acknowledgments section.


I suspect some of this is from the very defined notion of what constitutes authorship in medical journals, and the likelihood that someone who had some impact on the reported study would not make the authorship list. For example, the same ICJME that has developed the most widely used authorship standards also has this to say about non-author contributors:


  Because acknowledgment may imply endorsement by acknowledged
  individuals of a study’s data and conclusions, editors are advised to
  require that the corresponding author obtain written permission to be
  acknowledged from all acknowledged individuals.


Basically, the assumption is that, by being acknowledged, there is the possibility that you could be seen as endorsing the findings of the study, and that erring on the side of caution, you should have to obtain permission before acknowledging someone.

This is even true for not medically-specific journals. Consider, for example, this entry from PLoS One:


  Authors are responsible for ensuring that anyone named in the Acknowledgments agrees to be named.