How Many Muslims are there in the US?

For a while now, we've been under the impression that there were 6 or 7 million Muslims in the United States. A scientific survey can only identify 2.35 million. What implications does this have?

I recent study by the Pew Research Center found out that there are far fewer Muslims in America than the Council on American Islamic Relations has alleged. Does this mean less threat of terrorism? Why would CAIR inflate the numbers? Investor's Business Daily has an opinion:

But it's a wildly inflated guess manufactured by CAIR, something the media could have easily refuted all these years if they dared — simply by deconstructing CAIR's unscientific methodology.

Until now, finding reliable data for Muslims in America has been hard because the Census Bureau does not survey creed. So CAIR's fuzzy math went unchallenged, even though the "respected scholar" it hired to lead its "study" wasn't a trained demographer. In fact, as a CAIR board member, he wasn't even independent.

Worse, the Muslim professor admitted the number he arrived at for CAIR was a "guesstimation" that magically and conveniently matched the size — and potential political clout — of the Jewish population in the country, also estimated at 6 million.

Until now, the perception was that CAIR spoke for several million Muslims and could rally them to boycott a company or to vote as a bloc to swing an election if it didn't get its way. Officials feared the group because they thought it could marshal an Islamic juggernaut. The threat alone has caused many to back down from criticism or policies CAIR didn't like.

I don't understand CAIR's motives well enough. Looks like I have found a new focus of study. Their web site seems pretty friendly, but I guess we'll see.