Badges? We don't need no stinking badges.
I am a contractor for a "high profile" sillycon valley company. They have nice access control devices for entering buildings, but after that I keep my badge in my pocket (not displayed) all the time. No challenges (yet).
The previous (other) "high profile" sillycon valley company had similar policies, but after the slot broke off of the badge holder, I did what a cube mate of mine dis, and kept in my wallet. To enter the building, I just brushed my butt next to the reader. Nobody complained there either.
Yes, the current place of work has LOTS of signs that say "No tailgating". I try to be a good boy.