Here’s one of the mistakes you’ll find on yahoo.com that makes you want to laugh or cry:
It’s so sad to think that there are adults out there, making a living as professional writers, who have not mastered the use of the correlative conjunction either…or.
This is not rocket surgery, people. The conjunction must join parallel elements, which means they must be the same parts of speech. To check if you’ve got parallel elements, read the sentence up to the or (omitting the either).
The defense secretary’s departure is a strategic play by the White House
Then read the sentence from the start of the sentence up to either and tack on the words after the or:
The defense secretary’s departure is he is being used as a scapegoat.
Sounds stupid, no? That’s because the either…or is joining a noun phrase (a strategic play by the White House) and a complete clause (he is being used as a scapegoat). Here’s one way to rewrite that sentence so that the conjunction joins two independent clauses:
Either the defense secretary’s departure is a strategic play by the White House, or he is being used as a scapegoat.