grammatical number - Is this an inversion? If so, why would you use an inversion in this case?

Here's a quote from a CNN transcript, wherein a consumer psychologist says the following:
"What is relatively new are shoppers turning on other shoppers."

If "what is relatively new" were the subject, she would have said "is" as opposed to "are". Hence, it's an inversion having "shoppers" as the subject. Am I right?

If I'm right, then the question: why use an inversion in this particular case? Specifically, why use "are" instead of "is"?

For the whole transcript, see: http://transcripts.cnn.com/TRANSCRIPTS/1211/22/cnr.03.html

I did some follow-up research on what-cleft construction and would like to update my question by adding the following:

Swan says in Practical English Usage at 130, "A what-clause is normally considered to be singular...a plural verb is sometimes possible before a plural noun in an informal style." And Swan shows this example: "What we want is/are some of those cakes." (Emphasis in original.)

According to Swan, therefore, both "is" and "are" are possible, correct English in his "cakes" example. Also, he states that "are" is an informal style, which means that "is" is more formal.

Do you guys agree with this and is this applicable to my CNN example as well?