When you think someone is completely trustworthy and a nice person to whom you can tell all your secrets, but then they betray your trust and stab you in the back multiple times.
You: Hey that Brett Brookstone looks like a pretty nice guy!
Me: Whoa there buddy, he's brookstoned some other people before.
Means Heroin and is also a famous song by Guns N Roses on their debut album "Appetite for Destruction". When they are saying "Dancing with Mr. Brownstone" it means they are "Shootin Heroin"
"We Been Dancin' with Mr. Brownstone He's been knockin he won't leave me alone"