This has largely worked out with Postgres. The trick is making sure you have a few different competing corporations so that they can't force through anything without convincing all their competitors to support them. If done right the corporations end up paying for maintainers as well as to develop universally useful features. It's better not to have the corporations involved, but if they're going to be involved it's better to have as many of them as you can get. The worst case scenario is only one or two corporations being heavily involved.