No. SpiderOak will scan the file and find only the changes, and store new data blocks for those areas of the file. This means that SpiderOak is able to store all historical versions of a document using little additional space.
For example, if you're working on a research paper, and add new sections, charts, and other information to it as you go along, SpiderOak just stores these additional items. So, SpiderOak will be able to store all of the historical versions of your research paper using about the same amount of space as would be needed to only store the most recent version.