The Milky Way is moving at 630 km/s relative to the local Hubble flow, according to Wikipedia which is 1.4 million miles per hour.
Perhaps this puts the 2 million miles per hour into a different context.
Also, this story as reported on a NASA web site at
http://www.nasa.gov/centers/goddard/new ... _flow.html states that
"The clusters show a small but measurable velocity that is independent of the universe's expansion and does not change as distances increase," says lead researcher Alexander Kashlinsky at NASA's Goddard Space Flight Center in Greenbelt, Md.
Yes, they quote the 2 million miles per hour number but they themselves say that this velocity includes only a "small but measurable" additional, unexplained velocity.
And as Chris says, it's one set of observations, one study. I think that this is a bit of a leap as well
What's more, this motion is constant out to at least a billion light-years. "Because the dark flow already extends so far, it likely extends across the visible universe," Kashlinsky says.
To say that being constant over 1 billion light years when the observable universe encompasses 6 billion light years seems like a lot of enthusiasm.
Who know what else they will find?
They discovered "The Great Attractor" in the 1970s and then in 2005 they reported that it had 1/10 of its originally estimated mass. If I remember correctly, they think that this great attractor is a very large, old galaxy cluster. Perhaps we have an even bigger, even older one here, who knows?