Mercury Insurance is a very black and white company. They will want to know everything about you because they are very careful with their risks. DON'T try to hide anything from them because they have been doing this for 50+ years, have been taken to court by sneaky lawyers who try to get them to pay for things they shouldn't. So they are pretty good about only paying out on what they agree to pay out for on their contracts.
Lawyers don't like to deal with mercury because they are that good. Because they are that good and don't have to pay out fraudulent claims they can offer lower rates. However there are other companies that have faster claims service, but you will pay more for them.
I have mercury.
Treat them right and they will take care of you.
Just make sure you get enough coverage.
EDIT: Insurance companies don't bail out of claims, the general public is usally mis-informed about their policy and think they have something they don't. Majority of the time you hear bad Insurance stories you are not getting the full story.