Either a missing word or an extra word

It’s a minor omission on the Yahoo! front page — except to those who love the symmetry of a correlative conjunction:

The correlative conjunction is either…or, two words that when used together join two elements that should be parallel; that is, they should be the same part of speech. And each part should be able to complete the sentence they’re part of. So, “a LinkedIn” should be paired with “a Last.fm.” That’s it. I’m done being all grammatical on you.