Hi,
I don't believe that the eBay workers/sellers would be a good fit for the National Writers Union, UAW Local 1981. I took a few days to chat with some people about the idea before responding, and what we came up with was this: the NWU represents people who sell their writing, not goods sold by their writing.

I think that bloggers and people who write for the web, however, are perfect the NWU -- and should seek membership. Though I am not officially an organizer with the union, if someone needs assistance getting in touch with the right people at the union, feel free to email me: richard@unionreview.com.

Now, back to the eBay sellers. I want to think that one through a little more ... maybe there is an existing union that would work for them; maybe OPIEU? I know that reaching them with a message about organizing will be a long and tedious job, but one that would be well-worth it in the end.