Actually this wouldn't work for single moms and college students (at least for many of the offers), because they require a relatively high expenditure of money within 90 days on each card.
This is why I don't alert people like Ken Scalir to this approach.
Perhaps that's what Shizzmoney meant by his "NeoFeudalism" comment.
My attitude is, "If I'm going to spend this money anyway, why not get something back for it?"