Expanded background checks will be abused.

First instance of abuse is where the background checks are used to create in illegal national gun registry.

The powers that be... can also lower the bar so that a person with a small misdemeanor for a bar fight back when they were in college is considered a prohibited person. In some states / cities excessive speeding or downloading a lot of music can get you a felony charge. Felonies are no longer restricted to violent crimes. How long before spitting on the sidewalk prohibits you from owning a gun?

Then they have the whole domestic violence side they are trying to stretch to include just grabbing someone's wrist or shoving someone out of your way as you walk out the door. No end to the amount of abuse that background checks will eventually lead to.

In NYC if you have a gun permit, the police randomly call your house and ask your family members if you every display any signs of stress or great anger... and then pick at that. The wrong answers by your family will get your permit revoked. Bloomberg would like to expand such tactics to the rest of the country.