It should be a condition of download for Drupal that users acknowledge that they must not collect sensitive information in webforms without a lot of prior preparation because it will be published publicly on their site. I wish I had known.
I have a drupal 6 site (which uses tcpdf) for which I discovered that one of my webforms, which was collecting personal information, did not have the "viewable by anonymous users" permission revoked for "access all webform results". Never occurred to me to even check that would be default behavior for an input form submission, that the submissions themselves would even have configurable permissions. Drupal was making lists of webform results, and the results themselves, viewable by default. Therefore, google indexed the webform submission lists, the submissions themselves, and then took the pdf versions, converted them to quickviews and cached everything. A user notified us that their submitted information was available in google search results.
We revoked anonymous access to those drupal nodes, deleted the data from the server, and installed webform_nosave and I thought the cache would expire naturally. But a user brought it to my attention a couple weeks later that their data was still cached and viewable.