The Daily Beast points out Herman Cain's unhealthy and childish obsession with a number:

In Chapter Nine of This Is Herman Cain—entitled “‘Forty-Five’—A Special Number,” Cain notes that his “conception, gestation, and birth all occurred within” the year 1945 (true of pretty much anyone born in the last three months of that year). He then launches into a detailed account of how “45 keeps on popping up as I go about the business of being elected—you guessed it—as the forty-fifth president of the United States of America.”

Meaningful signposts include events both past (in 1945, Reader’s Digest published a version of Friedrich von Hayek’s The Road to Serfdom, which Cain ran across last year and loved) and future (in 2013, the year the 45th president will take office, Cain and his wife will celebrate their 45th wedding anniversary.)

In some cases the digits 4 and 5 are only part of a figure, like the times when one of Cain’s weekly commentaries ran to 645 words or when the final leg of a campaign trip took place on Flight 1045 traveling at 45,000 feet. At times the 45 in question is only tangentially related to Cain, as when he cites a Las Vegas campaign event where he met a couple celebrating their 45th anniversary. And in one case, the key moment ultimately doesn’t have anything to do with 45 at all: at an early strategy meeting, Cain and two aides believed they were seated at table 45 in a restaurant, only to be told that there were only 43 tables total. Regardless, it all adds up to something big for Cain.

The 999 tax plan—4+5, 4+5, 4+5—could be, in part, borne out of Cain's magical thinking. Remember how horrified people were when they learned about Nancy Reagan's obsession with astrology? This is like that, only even more inane.