Bloomberg recently reported that Gamestop, JC Penney, Gap, and Nordstrom have all closed their Facebook stores.  Just to be sure I checked Nordstrom's Facebook page.  It is true, the shopping tab is gone.  In the summer of 2011, I walked out of Payvment's Palo Alto office blown away. They had more than 60,000 merchants on the Facebook Commerce Platform. But I was still intrigued about the proposi…