Web-based applications do great things for groups. For example, online word processors such as Writely store documents centrally and allow coworkers to collaborate on them at the same time, eliminating the common workgroup headache of keeping track of file versions and who has the latest revisions.
Some of this functionality can be had in standard productivity software, with an add-on product such as InstaSecure's new Live Documents for Microsoft Office. Live Documents puts access-control wrappers around your Word or Excel files. You can specify who can read, edit, or print a file, and even a date after which people can't access it at all. The tool synchronizes changes in files, and it prevents people from creating conflicting edits, since it locks all instances of a file for writing when somebody else has it open.
Live Documents looks useful, but in a pre-Web way. Multiple users can't simultaneously edit a document, as they can in Writely. And the product requires a 2.5MB download to work inside Office applications. Without it, people who receive your documents won't be able to open them. As TechCrunch notes, it would be much more useful to be able to create a document in Word, then allow others to edit it in a Web browser. I said this in my AllPeers write-up, and I'll say it again here: Requiring recipients of a file to download a permanent plug-in limits its acceptability, especially in a business setting.