I see a lot of comments here talking about unfairness of this system, about how it would mean less motivation, etc... and general comments about wealth redistribution.
First, this program would not create additional welfare dependants. Instead, it would transfer SNAP recepients, able individuals living on social security disability payments (http://thelastpsychiatrist.com/2011/09/how_to_be_mean_to_you...), to a system that is market-based, less expensive, and (relative to the current system) creates incentives to join and/or stay in the labour force (you don't lose eligibility for this system the moment you get a job).
Second, overall welfare programs for the poor do not cost Americans nearly as much as entitlements for the middle classes (medicare, ACA, social security, etc...). So if you're a doctrinaire libertarian/conservative who is unhappy that any taxation/wealth transfer exist, then you should work towards eliminating these programs before going after SNAP, ACA, or opposing reform like this.
There's been multiple structural shifts over the last century: the second industrial revolution, de-industrialization, and now job-less recoveries (see Tyler Cowen's "The Average is Over" and "Great Stagnation" for discussion of the later).
As nearly all jobs work becomes knowledge work (as many have -- e.g., move to CNC for metal and wood working), each technology change means a bulk of technical knowledge becomes obsolete. This leads to a bimodal employment structure: those with the right technological knowledge (as well as those at/perceived to be at the top of the talent curve) are rewarded extraordinarily (driving up housing prices), while those without the appropriate knowledge and who are unable to re-adjust fast enough (e.g., currently there's a resurgence of C/C++ programming, but yet we've got a generation of programmers who have never bothered to learn manual memory management) have to settle for lower wages until they're at a point where the salary they will need to convince them to (again) take up full-time employment will not be a salary any employer will pay. As a result you'll see many workers working just enough to get by (remote freelance/consulting work) and then eventually drop out of the labour pool altogether. A wise welfare state policy should then be designed not to punish those with volatile incomes and encourage continuous labour pool participation (until the workers gained the technical skills needed for higher wage jobs, or perhaps the skills they've already had have suddenly become in-demand).
Eventually, I think this work itself out: settlement of inland west, cheaper housing construction techniques, a general socialization of the values of an entrepreneurial workplace (vs. workplace of "company-men"/"company-women") means there will once again be a middle class. However, I am very much scared of the many stupid things an electorate desperate "to do something" coupled with rent-seeking businesses might end up doing (that will cause serious long-term damage to this country) in the meantime. Any move from a system that is a mess of regulation (navigable best by those with "pull") to one that is more market-based would help.