Al Qaeda considered attacking the U.S. rail sector on the 10th anniversary of the September 11 attacks.
U.S. government officials said...some evidence was found [in Bin Laden's compound] indicating the al Qaeda leader or his associates had engaged in discussions or planning for a possible attack on a train inside the United States on September 11, 2011.
When the TSA extends its loving attention to the rail system, the same ridiculous children who say "you don't have to fly!" will be saying "you don't have to get on a train!".
When it starts trying to "secure" the interstate highway system--which, by its nature, will necessarily be a halfassed program with maximum intrusion and minimal benefit--they'll say "I don't know what the problem is; this is standard procedure at airports and train stations".
People who think the slippery-slope argument is a fallacy aren't paying attention.