There are bound to be at LEAST 5000 terror sympathizers in this country with contacts as diverse as the commie insurgents in the Phillipines, the questioanble Saudi supported "charities", to british bred terror scum, etc etc. The number seems small to me.
"Sympathisers" usually far outnumber those who either take any action or communicate with those who do. There are a few hundred million AQ 'sympathisers' around the world. If there are 5000 that have actually taken some action that would subject them either to a FISA warrant or the standard of 'reasonableness' you have expressed, I'd be amazed. I'd also think we need to be making lots of arrests.