In the beginning—about 12 years ago—there were structured data, and it was good.The correct answer is absolutely nothing. The word data is plural. Datum is the singular.
It irks me when the word data is used as the singular. One might have a single collection of data.
A collection of data is.
This isn't hard. Kudos to Ars for getting it right, even if the sentence is unwieldy.
EDIT: they have since uncorrected the article to introduce the error of a singular data.