Negative points
 

Looking at the points classification for races, some riders have negative points. How do they achieve this dubious honor? Is it assigned by officials for doing something slightly illegal, such as holding on to the team car uphill? I assume that it's not for being a poseur or having a bad hairdo. :)

Negative point sprints :D

Cedo,

You nailed it in your question. Points can be deducted and time added for infractions. If you otherwise have no points you end up negative.

A couple of years ago in the Tour a couple of riders for one of the teams were penalized time (I pretty sure in a Time Trial). They had been slow anyway, but the time penalty put them outside the cuttoff and they were eliminated from the Tour.