OK... but when you are dealing with a lot of laptops, enough to necessitate more plugs than a single 5-8 port power bar, it's probably going to run up against that limit.
I think the danger outside of load would be rare, but IIRC US specs for power cords specifically don't require compliance with daisy chaining (similar to C undefined behaviors?) and I bet most commodity power bars are cost-optimized to all hell.
Either the wires can handle the load or they can't. "Daisy chaining" is forbidden primarily because people are ignorant and the NFPA and OSHA are very conservative.
Even the $4 things I picked up out of a Fry's bin one day are 14AWG -- in other words, 10a@120v for 75+ feet, even through aluminium(!) wire, is still under 5% voltage drop.
I've bought nothing but the highest-end model of Apple laptop for years. I've never measured more than about 100 watts even under load with charging, the power adapters aren't even rated for more than about 1.5 amps on the input side. You're not going to have 10 people in a row gaming on 15" MBPs at one of these events.
The best reason not to do it has nothing to do with safety. It's that if there's an inspection and/or anyone reports it, you risk an abrupt drop in your bank balance.
(Also, I just tried, I can't even make a charged late 2013 MBP with a bunch of crap plugged in go over ~0.7amps off a 122v supply, the CPU actually throttled below rated speed to prevent it!)
I think the danger outside of load would be rare, but IIRC US specs for power cords specifically don't require compliance with daisy chaining (similar to C undefined behaviors?) and I bet most commodity power bars are cost-optimized to all hell.
Disclaimer: I am not an electrical engineer.