[Cu Roi]

The spokesman said he could not provide a copy of any of the letters. Kind of hard to show hard copies of something imaginary isn't it.

Perhaps the reason they cannot provide a copy of any of the letters was because the FBI was performing tests on them, as stated in the article?

[Brookhaven]

The reason some people are questioning this is because it doesn't fit the pattern of the other targets of the attacks. Major buildings, government offices, major media. All designed to get the maximum coverage in the news (look at how NBC is fixated on the antrax found in their office). Somehow planned parent clinic or office doesn't fit that pattern (a hospital would, but a clinic?)

The other reason is the radical fringe left (I'm not talking about liberals in general, but the far left fringe) have a history of faking incidents making them appear as victims. False campus rapes, false reports of racial slurs written on doors, false reports of gay bashing, you can do an search engine search and find a pretty big list.

Of course, it is possible that someone on the fringe right (again, I'm not talking about conservatives in general, but the fringe that both sides have to deal with) may be sending these also.

I think it is most likely someone on one of the two fringe groups (left or right) is sending these.