What grounded says is correct.
Lets look at a few figures. Standard 120V outlets are good for up to 15 Amps. So each group (branch circuit) of outlets would be put on one 15 Amp breaker. That way, no single outlet could be overloaded by the hypothetical hairdryer.
Some engineer probably figured that the average laptop load is 40 Watts (0.33 Amps at 120V). So one branch circuit can support up to 45 outlets. That comes to 9 circuits to support 405 outlets. That's 15 * 120 = 1800 Watts per circuit, or 16.2 kW total. Not insignificant, but that's something that can be handled by most modern aircraft utility buses.
Given some high load transient conditions, the seat power outlets are probably shed temporarily. From the user's point of view, unless their laptop battery is dead flat, they'll never even notice.
