According to Google's webmaster site:
"Syndicate carefully: If you syndicate your content on other sites, Google will always show the version we think is most appropriate for users in each given search, which may or may not be the version you'd prefer. However, it is helpful to ensure that each site on which your content is syndicated includes a link back to your original article. You can also ask those who use your syndicated material to block the version on their sites with robots.txt. "
So it seems that Google DOES see syndicated articles on article banks as duplicate content. While they may not penalize your own site for this, putting your article in the article banks probably won't increase your SEO rankings either. In addition, the search engine may show, in their search results, your article on the article bank's site instead of on your own site.
On the plus side, having your article show up in the search results often can lead prospective customers back to your site. I'm not abondoning my plans to syndicate my articles, but I will be creating two versions of the same article to avoid the duplicate content problem: a long one to put on my own site, and a short one to put on the article banks and on my blog. Taking the extra 15 minutes to shorten an article seems like a worthwile investment of my time.