Insurance is supposed to serve as a safety net, but sometimes that net has some unexpected holes. Even if you have full car insurance coverage, you could have less protection than you think because of exclusions and limits lurking in your policy's fine print. Car insurance policies can vary considerably when it comes to who's covered and when. "Insurance is not a commodity," says Bill Wilson, associate vice president of education and research for the Independent Insurance Agents & Brokers of America. "Buying an auto policy is not the same as buying a two-pound bag of sugar." Instead, he says, it's more like buying a bicycle. You have to evaluate features, the company's reputation and reliability and match the product for how you plan to use it. That's why it's not only important to compare car insurance quotes, but also to compare policy details before purchasing. "You should always ask for a full copy of your policy and read through the whole thing," says Penny Gusner, consumer analyst for Carinsurance.com. "It's better to know what coverage you have than to find out you don't have the coverage you need after something bad has happened." Here are six examples of how coverage might be less than you expected.