This is most likely because the forecourt fuel they've filled up with is Ethanol E85 - (85% ethanol, 15% petrol to help with cold starting) These fuels aren't suitable for 'standard' mapped cars and also are more corrosive (although the long-term effects of this are unknown RE seals and fuel lines).
A car running on E85 has to be mapped to run much, much richer than standard and you can imagine the consequences of running it on a standard mapped ECU.
So if they've bosched some out on the forecourt, they're stuffed. Dave Walker commented on it in PPC this month - Sainsbury's had it out and everyone was leaving on towtrucks, as they'd just seen the cheap price and bought it, then promptly killed their cars.
Just a warning peeps
Do NOT fill up your Dolly with it!
(Some top "fuel"ers
)