Textflow is an online tool to help people manage comments and changes to documents from other people. The product has not yet been released, but is in development from a company in Sweden. Their website has a video demonstration of the product in action. From their FAQ and screenshots it appears that the product is written with Adobe Flex.

Here's a description of the technology, from their site:

To make parallel word processing possible, we have developed WeaveSync – a new technology to index, match and synchronize documents and other sequential file data (patents pending). WeaveSync replaces the single document with hundreds or thousands of database elements: paragraphs, sentences and words. By comparative pattern recognition and statistics, WeaveSync analyzes the new version(s), finds changes from your version and pairs them with your source text. If content has moved, WeaveSync traces the move. Whatever changes in your colleagues’ document versions, WeaveSync connects it to the original. No version heaps, no mailed descriptions, no manual coordination work.