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?

This is an example of ‘clefting’, described in the ‘Longman Grammar of Spoken and Written English’ as a sentence in which ‘the information that could be given in a single simple clause . . . is broken into two clauses, each with its own verb.’ More specifically, it’s a wh- cleft, and wh- clefts ‘have a double emphasis: they give some emphasis to the opening nominal clause as well as to the element in final position.’

‘The Cambridge Guide to English Usage’ asks whether in such sentences the verb in the clause after the be clause can be in the plural, and gives a very clear answer: ‘Yes, and in fact it should be, if its subject is plural’. In an uncleft version, the sentence would be ‘New shoppers turning on other shoppers are new’. That is admittedly an unlikely sentence for anyone to say, but it does make it clear that the sentence concerns several shoppers and not just one.

On CNN, a spoken medium, this is acceptable, or at least accepted. But if you wrote a similar sentence in a formal essay such as an academic paper it would not be.

The example you cite from Swan, What we want is/are some of those cakes, is not precisely parallel with the CNN quote. In the Swan example the user waffles understandably between having the verb agree with its subject, what (singular), and having it agree with its object, some of those cakes (plural). Substitute a pronoun for the object, and the ambiguity is patent:

What we want is/are those.

This is not so with your original example, from CNN. There both the subject and the object are singular, as Bill Franke remarks: it is not the shoppers which are new but their turning on each other. Again, substitute a pronoun:

What is new is that.

The CNN writer has allowed the plural subject of the object clause to infect the adjacent verb.