Why would the FBI tip off Islamic leaders in advance of their raid on Islamic Extremists?

The news of the FBI raid on the radical bunch of Islamic extremists planning a violent conspiracy has been pretty well reported. The FBI did a darn good job, all the FBI agents are thankfuly safe (except unfortunatelt for an FBI dog which was killed) and most of the suspects are in custody. So it's a win for the good guys.

There are some questions about the raid though.

If these particular "radical" Islamists, have nothing to do with mainstram Islam, why then is the head of the puported-to-be-mainstream American-Arab Anti-Discrimination Committee being briefed on it in advance and then why is he concerned about the FBI use of informants in mosques?

Imad Hamad, regional director of the American-Arab Anti-Discrimination Committee, said Arena briefed him on the raids late Wednesday afternoon. The case has renewed concerns about use of FBI informants inside mosques, Hamad said.

"So far in this particular case, we don't have any of the facts but what the government said," Hamad said. "It is premature to render any judgment."

Also, if this sect is not "mainstream", why was the Muslim Alliance in North America having the chief suspect Luqman Ameen Abdullah, who was kiled in the raid

"on an advisory board for the Muslim Alliance, and he often met with local imams, said local Muslims.

Indeed, Why is the FBI tipping off Islamic leaders prior to a raid?

Doesn't this increase the chance that a sympathetic co-religionist would tip off the subject of the raid thus resulting in them going into hiding or otherwise destroying evidence, not to mention giving them an opportunity to ambush FBI agents, completely and unecessarily putting these agents' lives in danger?

Also isn't it funny how mainstream Muslims are concerned that there may be informants among them that might report criminal activities to the FBI?

Hamad said he and other Arab-American leaders have had ongoing talks with the FBI about its use of informants, and authorities insist that they use such sources only when they have specific allegations rather than during a “witch hunt.”

Still, the tensions will be aggravated by this week’s events. And those who already are skeptical of the FBI’s tactics will doubt the allegations contained in the indictment.

“The case – regardless of the facts, regardless of the allegations, regardless of what went right and what went wrong – brings back that issue of informants,” Hamad said.

How about this - don't commit criminal conspiracies against America and you won't have to worry about informants reporting on your nefarious plans to the FBI?

One would think mainstram muslims would encourage the reporting of criminal acts to the lawful authorities of this country, but apparently not.