Probably illegal aliens - like Obama’s aunt.
The IRS defended its interpretation of the tax code, which states that illegal immigrants who pay no taxes are eligible for the tax credits. Filtering out who is not eligible is the problem.
...A chart in the Treasury Inspector Generals July 2011 report shows a rapid rise in tax refunds that went to ITIN holders, who were four times more likely to request the child tax refund compared with those with Social Security numbers. In five years, those refunds quadrupled. Despite that, the IRS didnt budge and said it planned to keep paying until Congress tells it to stop.
Much more by following the link including that the state of North Carolina manages to crack down on this stuff, but the Feds proudly pay out to anybody who files a return early and often.