I don't disagree with any of this, but the fact is that airlines do allow laptops to be used during flight, and one assumes they have done some sort of risk analysis, and most laptops have LIPO batteries.
I suspect that the risk of this is very low with any normal consumer product. Model plane batteries have been known to go incandescent more often but I think that is for a number of reasons
- they are charged at very high rates (a lot more than 1C in some cases)
- they are discharged at huge rates - 100A is not unusual
- they get a lot of physical hammering - when a model crashes, it could be 100s of Gs, and I know that often the battery is totally smashed, but if it is still "apparently" working the owner is not going to chuck it away because it probably cost £100
- I don't get the impression that model plane bits are of particularly good quality - they are constantly packing up...
To minimise the risk, I also tend to not charge batteries during flight. I tend to keep the device(s) charged so even though the supply is connected, the internal charger turns off ASAP.