Jessica Enders wrote an article on A List Apart about an experiment she did to determine whether "zebra stripes" are helpful.
The conclusion was zebra stripes don't help, but they don't seem to do any harm.
This experiment yielded no evidence that zebra striping consistently improves the accuracy or speed of tasks. This would seem to suggest that we shouldn’t bother with zebra striping anymore.
However, there are a few arguments against tossing zebra striping out altogether.
That was just one study. Formulate Information Design was supposed to have done a follow-up study, but I couldn't find any information on it, so I sent them an email with a link to this question.