CMS has been cracking down on violations by Medicare plan operators of late, and has handed out $770,000 in fines to 11 companies since March. Violators have included big names like UnitedHealth, Humana and WellPoint. UnitedHealth, for example, was accused of failing to supervise marketing representatives and improperly denying claims without giving proper explanations to beneficiaries. Humana has failed to keep up with complaints about marketing and has not handled claims denials appropriately, the agency says.