Thought this might be of interest, since the concept has been discussed periodically, including in the "Travels with Bruno" thread (Cool FIRE article in MSN Money - Page 7 - Early Retirement & Financial Independence Community
Here is proposal by Charles Murray, "A Guaranteed Income for Every American: Replacing the welfare state with an annual grant is the best way to cope with a radically changing U.S. jobs market—and to revitalize America’s civic culture." (In WSJ: google that title and you'll be able to read it all.) A snippet:
The UBI is to be financed by getting rid of Social Security, Medicare, Medicaid, food stamps, Supplemental Security Income, housing subsidies, welfare for single women and every other kind of welfare and social-services program, as well as agricultural subsidies and corporate welfare. As of 2014, the annual cost of a UBI would have been about $200 billion cheaper than the current system. By 2020, it would be nearly a trillion dollars cheaper.
Has phaseout, but no one gets less than half the base rate, so as to decrease the hit of no Medicare or Social. Transition rules would be extremely complex, even if it had a better chance than the proverbial snowball in Hades.