Victoria Toensing writes in National Review Online:

"The talking heads mistakenly surmise that because treason cases are rare, they are difficult. No, they are rare because they can only be brought when we are in a military conflict. The fact that there have been limited time periods when one could 'levy war against' the United States does not make the case more difficult when such conflicts do occur."

There is something to this, but the U.S. has fought a lot of wars, and some have gone on for quite a few years. Surely treason prosecutions are also rare for the same reason that bestiality prosecutions are rare. I can't find a link now, but a few months ago there were a lot of news stories about a man somewhere in New England whose father had beaten him senseless with (I think) a tire iron because the son wanted to marry his (the son's) dog, and had already, so to speak, consummated the relationship. The son even tried to bring the dog to court with him as his wife. Although there are exceptions, I would say that marrying your dog and betraying your country are crimes that relatively few Americans have ever wanted to commit, or, I imagine, ever will. Finally, while I do not condone beating one's son with a tire iron even in cases of treason or bestiality, Sulayman al-Lindh's father seems to have gone a bit too far in the opposite direction.