Getting an array of all VcFolder objects in a datacenter?

I have what I thought was a simple problem, but I can't figure out how to accomplish it. I need to get an array of every VcFolder object inside a datacenter. What's the best way to accomplish that? (This is in a multi-datacenter vcenter, that might be relevant.)

Bonus unrelated question, how can I get the username of the current user running a workflow?

Thanks!