Is this just a confirmation of what many of us here suspected all along, that the interview process is way to late in the game to correct for diversity?
If so, this could be a manifestation of the high attrition rates for experienced female engineers.
There are plenty of posts out there about why Facebook's recent declaration that their numbers are that way due to the pipeline problem is wrong. There was a particularly good one I recall, but I can't find it sadly. But the other articles out there should suffice too.
There are also many self taught programmers out there, which are not affected by the "pipeline". Interview practices often subconsciously discriminate against them (for example, an overabundance of datastructure questions -- most self taught programmers I know are good enough with datastructures, but haven't become super awesome experts at them because that's not very useful when actually programming. Focusing your interviews on solely these questions excludes nearly half the "pipeline").
The college I was in has an extremely skewed gender ratio. There are many companies out there that nearly exclusively hire from a set of similar colleges as a matter of prestige. And of course have a large gender diversity issue, which they (well, employees there -- in this country there is less of a push for diversity and companies don't make public statements about it) blame on the pipeline. This is absurd. What Facebook does is similar, though not as stark.