(this is a repost from http://tableau7.wordpress.com/2012/03/31/tableau-reader/ )
Tableau made a couple of brilliant decisions to completely outsmart its competitors and gained extreme popularity, while convincing millions of potential, future and current customers to invest own time to learn Tableau. 1st reason of course is Tableau Public (we discuss it in separate blog post) and other is a Free Tableau Reader, which provides full desktop user experience and interactive Data Visualization without any Tableau Server (and any other server) involved and with better performance and UI then Server-based Visualizations.
While designing Data Visualizations is done with Tableau Desktop, most users got their Data Visualizations served by Tableau Server to their Web Browser. However in the large and small organizations that usage pattern is not always the best fit. Below I am discussing a few possible use cases, where the usage of Free Tableau Reader can be appropriate, see it here: http://www.tableausoftware.com/products/reader .
1. Tableau Application Server serves Visualizations well, but not as well as Tableau Reader, because Tableau Reader delivers a truly desktop User Experience and UI. Most known example of it is a Motion Chart: you can see automatic motion with Tableau Reader but Web Browser will force user to manually emulate motion. In cases like that user advised to download workbook, copy .TWBX file to his/her workstation and open it with Tableau Reader.
Here is an example of the Motion Chart, done in Tableau, similar to famous Hans Rosling's presentation of Gapminder's Motion Chart (an you need the free Tableau Reader or license to Tableau Desktop to see the automatic motion of the 6-dimensional dataset with all colored bubbles, resizing over time): http://public.tableausoftware.com/views/MotionChart_0/Motion?:embed=y
2. When you have hundreds or thousands of Tableau Server users and more then couple of Admins (users with Administrative privileges), each of Admins can override viewing privileges for any workbook, regardless of designated for that workbook Users and User Groups. In such situation there is a risk for violation of privacy and confidentiality of data involved, for example for HR Analytics and HR Dashboards and other Visualizations where private, personal and confidential data used.
Tableau Reader enables additional complementary method of delivering Data Visualizations through private channels like password-protected portals, file servers and FTP servers and in certain cases even by-passing Tableau Server entirely.
3. Due popularity of Tableau and ease of use, many groups and teams are considering Tableau as vehicle to delivering of hundreds and even thousands of Visual Reports to hundreds and may be even thousands of users. That can slow down Tableau Server, decrease user experience and create even more confidentiality problems, because it may expose confidential data to unintended users, like report for one store to users from another store.
4. Many small (and not so small either) organizations trying to save on Tableau Server licenses (at least initially) and they still can distribute Tableau-based Data Visualizations; developer(s) will have Tableau Desktop (relatively small investment) and users, clients and customers will use Tableau Reader, while all TWBX files can be distributed over FTP, portals or file servers or even by email. In my experience, when Tableau-based business will grow enough, it will pay by itself for buying licenses for Tableau Server, so usage of Tableau Reader in n o way is threat to Tbaleau Software bottom line!
Update (12/12/12) for even more happy usage of Tableau Reader: in upcoming Tableau 8 all Tableau Data Extracts - TDEs - can be created and used without any Tableau Server involved. Instead Developer can create/update TDE either with Tableau in UI mode or using Tableau Command Line Interface and script TDEs in batch mode or programmatically with new TDE API (Python, C/C++, Java). It means that Tableau workbooks can be automatically refreshed with new data without any Tableau Server and re-delivered to Tableau Reader users over ... FTP, portals or file servers or even by email.