Because one of them might turn out to be Al Sharpton.
In what has to be one of the oddest criminal law stories I've seen for a while, Al Sharpton, who yesterday denied that he had been an FBI informant in the 1980's, today admits it and says it's old news.
I was a federal prosecutor for many years, and I can tell you that informants are necessary, particularly in mob and big drug conspiracy cases. But they're a boatload of trouble. For one thing, anyone in a position to have lots of information about extortion rackets or drug dealing is unlikely to have the character of the Pope. The defense lawyer in cross examination is going to go to town.
For another, such people are likely to have been life-long fabulists, and Big Al is no exception. Indeed, Rev. Sharpton is the prototype liar, having concocted one of the most remarkable hoaxes of recent times in the Tawana Brawley rape hoax.
None of this, of course, keeps Big Al from being a frequent, honored guest of Barack Obama. Records show that Sharpton had more visits with the President last year than Harry Reid. Gads, I hope he wasn't wearing a wire!
UPDATE: One acid commenter on Powerline notes, "Considering that Al ratted on the mob, he should be as nervous as a virtuous intern at the Clinton Foundation."