Given all of the utilities out there to convert .csv files to DW tables (or use them directly in DW, like the CSV plugin http://www.dokuwiki.org/plugin:csv
) this should be a relatively simple plugin, but my minimal PHP skils were last used almost 12 years ago, and likely are not up to the task, so I ask for your help!
The way this works (in my mind at least) is the user simply surrounds a table in the wiki with a tag (<tocsv></tocsv> perhaps?) Any table inside this tag would have a button added next to it (small button similar to the "edit" button in each subsection) to convert the table to a csv file and send it to the user through the browser's regular "save file" function...
Looking at the CSV plugin's syntax.php file, it seems it would be reasonably easy to just reverse the order of processing in that plugin (taking the DW markup as source, and find/replace needed characters to spit out .csv) using php to serve out the file for the user to download is also relatively simple. That just leaves creating the button to be embedded next to the table to fire the process off.
Another possibility would be to use something like Jquery table to csv http://www.kunalbabre.com/projects/table2CSV.php
to grab the HTML formatted table after DW has rendered the page, though to me this does not feel as "right" as using DWs existing infrastructure to do some of the work...
I'm willing to help in this as much as possible, though as I said my PHP skills are rather limited and probably out of date ;-)
Some clarification on my reasoning for this...
To pick one example, we have a contact list set up as a table in our wiki. there is some overall management of course, but generally, the individual users keep this table up to date (when they move desks or get a new cell phone for example). Most of our users are not terribly computer literate. So I use FCKGLite as a WYSIWYG editor. This makes it much simpler for the users to make changes to tables, especially. With the turnover rate in our business, this table changes quite frequently. Using the CSV plug-in makes editing the table inside of the wiki either impossible (if using a linked file) or impractical to less savvy users (if using inline data) so I really need to keep the ability to edit the table in FCKGLite. However, it is incredibly useful to be able to grab that information as a csv file (on the fly, so you get the most recent version) to be imported into... well.. just about any other program... Thus, the quest to just have a button to send the user a csv file of the info in a table.
Hope that helps to clarify things more than it confuses them!