Google should make a point that the maps aren't truly free, they are paid for by ads.
Just because the business model is different doesn't mean someone isn't paying for the service.
Considering Google kind of has a monopoly on the ads, that's where I see a big disparity issue. It's not the fact that they're giving it away "free" that's the real issue for me, but the fact that competitors would most likely have to use Google (AdSense) to get advertisers money to fund their own free product.
The real rub here IMO is how Google is poised to make money no matter what, even if you compete against them, you're still likely to help them earn money and it happens every day.
How sick and twisted is that?