And did the original contributors fork the project to a new successful initiative? Or if not, why not?
I'm also curious why companies feel the need for this -- if the data is all open in the first place, why do the companies even need to bother? Why don't they just use the data directly?
Without specific examples it's hard to understand.
That's not to say corporate involvement/sponsorship isn't important: it's vital to many important projects. The issue is when companies start trying to influence the projects beyond their technical needs and start trying to wrap their business model around them (a good indicator of that seems to be their involvement in governance) that the trouble starts. I think that's the concern being expressed about OSM.
This is a very old strategy. Companies (especially the large, name-brand ones) aren't getting involved because they believe in the mission/objectives of OSM but rather that they see a strategic advantage in their involvement. They dip their toes in, get entrenched and then make their move. It's a lot faster and less expensive for them than trying to replicate what the project has produced.