I remember we discussed this on the mailing list a
few months back and I just had a clear example of it, thankfully on a test
site.
I de-selected the Audio module (remember, as we are
advised to do when doing a major drupal version upgrade) and I saw the
message:
"The content
fields table content_type_audio has been deleted."
so this seems proof positive that following the
official advise to deselect modules can harm your site and lose you
data.
Neil