Oddly enough, there is a sign in the window at my dermotologist(SP) front window stating that they don’t accept the aarp approved United Health Care insurance.
Last year (2012 for 2013), I stayed signed up with the Medicare Advantage plan I had the previous year. Soon after the enrollment period started last October, I got a letter from SocialSecurity/Medicare. The letter stated that the insurer of my plan did not have very high recommendation marks and that I should consider changing plans. The plan 'recommended' by the letter was the AARP UnitedHealth plan.
Soon thereafter, I got a letter from my insurer stating that their rating was in the same range (3 stars) as other plans in my state and they planned to continue service and even add new features.
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That proved to me that SS/Medicare was instructed to break their own regulation which prohibits insurers from contacting perspective clients for the purpose of getting them to join a specific Medicare Advantage plan. Insurers can run general information ads, however.