If somebody wandered up to me in the street and told me they were from the future, I would think one of two things, either they are a first year drama student who is trying to involve me in some form of live street performance or they are batshit insane. Obviously those two things are not mutually exclusive, but chances are this particular individual would just be crazy. So if you are in fact a visitor from the future, chances are that if you tell someone who you are and why you are here, as is the case with Bruce Willis in 12 Monkeys, you will get locked up in the nearest nut house where you will be forced to hang out with a crazy Brad Pitt and eat spiders instead of attempting to stop humanity being pretty much wiped out.