A title which always annoyed me, because it should be "fewer than zero".
That is not necessarily accurate, in my opinion. "Zero" can be used colloquially to indicate "none" in opposition to "some." If the object in question is not made up of discriminate parts, such as "tolerance," than "less" would be appropriate. The phrase "less than zero" would in such a case merely emphasize the certainty of the lack of whatever.
Example: "I have less than zero tolerance for pedantic dweebs."
In that case, "fewer than zero" would be grammatically incorrect.
Of course, one might argue that neither "less than zero" nor "fewer than zero" really make any sense grammatically, since there is no amount of countable things smaller than zero outside the realm of math. It is similar to the case of double negatives. Some modern grammarians argue that double negatives are an allowable exception from normal grammar rules when used for emphasis, while other grammatical traditionalists argue that double negatives ain't never acceptable.
Maybe Dr. Pedantic has an opinion on this issue...
---
"And Wirthling isn't worth the paper he isn't printed on."