I don't understand the open identity

[floramon]

X-Men, Fantastic Four, Ronin, Captain America, Thor and some other heroes did not hide their identity. 

Iron Man movie: The truth is, I am the Iron Man!

Since now whole world knows Spiderman's identity, what will happen next? Can't he just stand out and declare "I am Spiderman!"?

OK, some may say "Because the enemies will kill Spiderman's best friends!"

But why nobody kills X-Men or Fantastic Four or other heroes best friends?

So far, Spiderman and Flash are two heroes whom did not take extra care about their secret identities. Compared to Batman, I really very rare saw him showing his identity in front of strangers, he only unmasked in front of Alfred only.