I believe the real driving force is thousands of Etsy sellers using Twitter (and Facebook) to share their latest items for sale with friends and followers.
So it makes perfect sense for Etsy to use its Twitter account to highlight those sellers, retweet their posts, and cultivate and curate the Etsy community on Twitter.
Fred Wilson, How Etsy Uses Twitter, from his A VC blog
Since I’ve often described Genlighten.com as “Etsy for Genealogy Document Retrieval”, it should come as no surprise that I see Etsy’s Twitter strategy as a perfect fit for us. As our providers Twitter about the lookups they offer, and post links to them on Facebook, we can in turn “cultivate and curate” the Genlighten community on Twitter. Thanks, Fred!