Imagine this scenario: One day, retail giant Wal-Mart decides that it’s going to open up a section of all of its stores to products devised by outside suppliers, as long as they meet some internal company standards for inclusion. They call this new service, “Wal-Mart Platform.” In advance of the launch of this new marketing opportunity, Wal-Mart quietly invites a bunch of companies as well as individual entrepreneurs to get in before the start, so that on launch day they have an impressive array of prominent participants. A section of Wal-Mart Platform is for causes, but they only invite one presidential campaign in early.

If this really happened, would it be ethical? would the Federal Election Commission deem it legal? Would campaigns from both ends of the political spectrum complain?

Although this is a fictional scenario, the giant social networking site Facebook engaged in something like it in the last couple of weeks, raising serious questions about how a private, but massively used, platform should behave in the brave new world of online politics.