Wood does have natural anti-bacterial properties.
I build custom cutting boards and chopping blocks from all sorts of hardwoods.
Not only does wood have these properties but there are physical reasons as well that makes them more safe than plastic ones.
Recent studies, in fact, indicate that while new plastic boards maybe safe, once they are used, bacteria builds in the cuts, and even running it through the dishwasher doesn't kill it off.
Plus, of course, wood is better for your knives because it doesn't dull them as plastic can.
Adding it all up, I don't understand why anyone would opt for plastic over wood.