Iran is looking to start a war. Having their navy vessels nearby is a threat but when combined with a recent article "Iran says it delivers new cruise missiles to navy" (http://world-news.newsvine.com/_news/2011/09/28/8015006-iran-says-it-delivers-new-cruise-missiles-to-navy), and a building threat becomes more apparent. Add in Irans nuclear endeavors and their religious fervor. We should be very wary of the potential nuclear payload of those cruise missiles.
Hopefully any Iranian military vessals sailing for the US coast will "accidentally" sink apart long before they come in range.