The siege on SAC capital continues.  The Government star informant, who cooperated with the authorities and provided them with the names of 20 people, he said had engaged in criminal activity, avoided prison on Wednesday after a judge sentenced him to probation.   The former analyst, Wesley Wang, secretly recorded telephone conversations and wore a wire in meetings with former friends and colleagues. His role in the government's inquiry, prosecutors said, has led to 10 convictions.

Judge Jed S. Rakoff, who presided over the sentencing in Federal District Court in Manhattan, said he spared Mr. Wang because of his exceptional assistance. "I take it that Mr. Wang's cooperation has been extraordinary," Judge Rakoff said. "Not just substantial, but going beyond substantial."

Mr. Wang, 39, is the latest government informant in the insider trading investigations to receive a noncustodial sentence. His lenient penalty highlights the benefits of cooperating.  At least two former SAC employees continue to assist authorities in their investigation of SAC.  They are trying to convince one more:

• Jon Horvath, a onetime SAC tech-stock analyst, pleaded guilty last fall and said in court that he traded on inside information along with his boss, Michael Steinberg, an SAC portfolio manager and top lieutenant to Mr. Cohen. 
• Another former SAC employee-turned-informant, Noah Freeman, also admitted to insider trading while at the fund. Testifying in a case last year, Mr. Freeman said he gave the government the names of 12 individuals he believed engaged in criminal conduct.
• Federal Bureau of Investigation agents have tried to gain the cooperation of Mathew Martoma, a former SAC portfolio manager indicted last month in a $276 million insider trading prosecution. The case, for the first time, ties Mr. Cohen to the questionable trades. Mr. Martoma has rebuffed the government's overtures and pleaded not guilty.