Negative guest reviews can have real consequences, say travelers who have received them. A host can refuse to rent to you, and a driver may not be matched with you. And since the system is so subjective and opaque, you may never know the real reason why anyone dinged you. Was it the house key you inadvertently took or some other faux pas? The review wars are unlikely to affect you if you're an occasional participant in the sharing economy and can easily switch to a hotel or rental car. But for the growing number of travelers who rely on vacation rentals and shared rides, it can be confusing, and a cause for concern. Get the full story at USA Today