Are presentations being stored or cached on end users machines?
Depending on how information is being presented in a web conference, some content is cached and some is not. When the presenting published PowerPoint, Word and Excel documents some JPEG and HTML content will be cached on users browsers. When sharing applications, the content is not cached in the local browsers. Please be aware that it is not possible to prohibit users from using third party software to capture and store any content which is displayed on their screens during your presentations.