I don't think a reasonable person would ever claim the technological equivalent of a right of rescission for data contributed to a community-collaborated document. Rather, people are taking exception to unconscionable clauses in the terms of service of Facebook, Google, etc. that effectively grant to each respective corporation a non-exclusive, transferable, sub-licensable, royalty-free, worldwide license to "use" any content posted on or in connection with each service. It's the overbreadth of the term "use" that people balk at.