I've been on projects (and I'm sure I'm not alone in this) in which some members contributed negative value.
To contribute zero a bad programmer would have to just sit around and reddit all day or whatever. Once the bad programmer starts writing code he is almost surely a net negative since eventually someone is going to have to rewrite his code and unless the code is completely decoupled from everything else, the time required to do that rewrite will exceed the time it would have taken if the bad programmer had never written any code at all.
To contribute zero a bad programmer would have to just sit around and reddit all day or whatever. Once the bad programmer starts writing code he is almost surely a net negative since eventually someone is going to have to rewrite his code and unless the code is completely decoupled from everything else, the time required to do that rewrite will exceed the time it would have taken if the bad programmer had never written any code at all.