Civil War reenactments are staggeringly expensive to stage. Even the small events require organizers to put in a full-time effort for many months--not something an employed person can do. When there are 15,000 reenactors, 125 cannon, and perhaps 60,000 spectators to organize, you can understand why corporate sponsorship is becoming necessary. Within the last few years we've seen that the people who enjoy this hobby want one big megaturbo-farbfest event each year. But if corporations don't foot the bill, they won't happen. And that means that many Americans won't have the chance to learn about nineteenth-century history and material culture through this medium.
That said, I have to add that as a reenactor I prefer the tiny by-invitation-only hardcore events during which we immerse ourselves in the life of the nineteenth century.
Yes. And I can't see these events costing that much. There is a Confederate church a few miles from where I live which puts on re-enactments every year with about (40) participating and no corporate sponsorship. It is a very high quality event which attracts a thousand or more.
The problem I see with corporate sponsorship is the corporate culture which will end up corrupting the events.