Bears are not pets, so keeping a bear would be a bad idea, and probably illegal in most states. Some people keep bears for entertainment purposes, showing them off in shows which promote interaction with the audience.
A number of incidents have been reported of bears kept as pets who have escaped or caused injury to humans. Bears become more aggressive as they grow older and captive bears may exhibit extremely aggressive behavior. Check out this video of a woman being attacked by her pet bear: Why Not to Keep Bears as Pets.
Most pet owners can’t provide adequate care for bears: housing, medical care, secure containment and nutrition. Additionally, they are usually unable to provide the social and behavioral requirements of bears. Bears kept as pets are declawed and go through painful dental procedures to make them less dangerous, causing great suffering to the animals.
If you are aware of someone keeping a pet bear in substandard conditions, report this person to local humane societies or animal control officers.