bash - shell events "!"

[Die Optimisten <inform@die-optimisten.net>]

Hello

echo hello!    # displays that, BUT:
echo "Hello!" # tells:
    -su: !": event not found    # this worked years before without problem!
Is that intended? These leads to errors in many scripts (including 
installig package dkms)
How can this be turned off? For me this behaviou should be changed,
 for example: Events should contain whitespace before or after it, or 
only work outside quoting...

using GNU bash, version 4.2.37(1)-release (x86_64-pc-linux-gnu)