webform duplicate submissions

Is there a known problem with Drupal losing/corrupting SESSION variables for anonymous users when caching is active?

If there is, could someone point me to some detailed info? I've searched around quite a bit and found scattered reports of people struggling to control this kind of SESSION data for anonymous users unsuccessfully, but I'm unable to find anything that conclusively explains why this is so.

Situation is this:

has anyone seen webform create duplicate, or even triplicate submissions?

i know sometimes users get impatient and will click more than once, also that fingers can just slip, but it seems we're seeing a lot more of this just recently related to some adjustments we made

seems like i've received dupes off drupal mailing lists myself before and am curious if there are obvious places to look to try to track this down