Interesting, could this be the beginning of something like WeChat for businesses, where every business function you think of can just be completed on Slack? I doubt there's anything about the U.S. market that makes these non-open / corporation controlled platforms undesirable (as some other comments suggest); after all, Windows dominates the business landscape. Its just a question of whether Slack can go from convincing start ups x,y and z to use these apps, to convincing Fortune 500 companies to take the plunge.