CharlyGordon said:yeah, what Kansei said. Some people swear by it... My car was running just fine before it, so i didn't notice a major difference. If for nothing else, it's kinda fun to watch all this white smoke (essentially steam) pour out of your exhaust (although your neighbors won't be too thrilled about it).
I always go to the wetlands when I do seafoam. My whole campus is on wetlands so I just find a parking lot in a secluded area in the middle of nowhere in the woods (i.e. the freshman dorm parking lot that's like a 20 minute walk from the dorms) and do it there. My roommate's volvo was near 200k miles when it had it's first seafoam treatment.. that thing shot out SOOOO much steam that we were sure someone must have alerted the EPA.