The online versions of the programs will lack many of the features found in the full versions found in Microsoft's Office suite of applications.
Google recently bought Writely to do just this (I used it to write and share my XPRL paper last week). It is an online word processing package that includes a co-authoring and sharing capabilities.
Writely, offers a range of services that competes with Microsoft. Gamil, calendar, spread sheets etc.
These capabilities are useful in PR practice but are also a lesson for us all to learn about how the Internet disintermediates existing business models.
Bloggers, as citizen journalists, have undermined the role of newspapers in a big way and this means they have also undermined the press relations communication models that is the predominant practice of many PR agencies and in-house departments.