The Washington Times is being widely linked for a story about how CAIR's membership has "spiraled down from more than 29,000 in 2000 to fewer than 1,700 in 2006." based on tax documents obtained by the WT.
Ostensibly this is because CAIR does not suitably critique or condemn terror attack. Assuming its true, that seems to be a quantitative measure of the moderation of the American muslim community. However I find that explanation rather unserious, since CAIR has been at the forefront of every public condemnation of terror that American muslims have made.A casual google search or review of CAIR's website makes this obvious. The one thing muslims can count on is that no amount of condemnation of terror is ever enough to satisfy those who insist that muslims have such a duty to do so; in fact muslims do not have any such duty whatsoever.
If there is a decrease in membership, it is probably more due to the routine bad press that CAIR gets and the foolishness of some of the national figures at the national organization leadership. However, on a per-chapter basis, CAIR is a solid organization with good people who do good works. If you ignore the bloviating of the ego-driven leadership at the top, who of course are totally isolated from the daily activities of the independent regional chapters, you will see a very different picture of CAIR emerge.
Of course, such a picture does not mesh well with the inclination of some to distrust any gathering of muslims for any purpose. The subtext is that CAIR is a vehicle for domestic terror and treason, and every piece of (bountiful) evidence otherwise is dismissed as taqqiya. The foundation for that is, of course, the sentiment (dominant on teh right, but not wholly absent from the left either) that muslims cannot be trusted, their numbers should be limited, and their freedom of expression of faith curtailed and monitored.