You honk your horn outside of your buddy’s Vinewood apartment. He walks out and hops in your Aston Martin-ish car. He gets control of your radio. “Put it back on WCTR talk radio, dammit,” you say. “I want to listen to Lazlow.” You drive a couple miles, park, and get out. You each equip masks and glasses from the unique-to-GTA Online inventory menu, and walk into a convenience store. One of you points a gun at the clerk behind the counter. You can actually scream at him through your chat headset in order to intimidate him, making the cash grab go faster. You speed away with the police in pursuit, but eventually lose them in a parking garage under some downtown Los Santos skyscrapers. With the heat gone, it’s up to your friend – the one who actually got the cash from the clerk – to divvy up the cash as he sees fit. He could give you 10%, but then you could simply stop the car, get out, shoot him in the face, and take all the money for yourself. Or, you know, you could just split it 50-50 like gentlemen.
On a related note, you’re able to insure your cars in case other players steal them. You wouldn’t want to lose that heavily modified, custom Cheetah you spent thousands of in-game dollars and lots of time tricking out, would you?