Haha this funny.
Is it that there aren't marshalls any more? Are they only employed by private clubs?
Anyway, I've defiantly noticed the zombie, types, oblivious to what's going on around them, let alone behind them. They also share the mentality that their round will be disrupted if they let you through. Sorta like the dh In the fast lane on the freeway. "Ima tax payer driver".
So, yeah the solution, I guess, is to go around them, middle finger out. Kidding.
Then there's the other type. These rockstars zip by you, while you're on the green and proceed to tee off . They're awesome, until they realize there's a group right in front of them. "Eff it, they're going for it." This is probably the twosome with a speaker, who have now created an awkward situation as they drive off while you pull up to the tee box.
My solution would be to have the starter as well as messages, signs and a plane flying over prompting you to let faster players through. There's a balance to this though and it can be tricky for some, especially when they're faced with multiple groups in front of them.