Consequences of leaving AC adapter (or any kind of adapter) plugged into outlet?

[mindstormer]

What are the consequences of leaving the AC adapter plugged into the outlet but without it being plugged into the advice? It seems like a hassle to unplug the device from the adapter and then unplug the adapter from the outlet every time. On some adapters, leaving it plugged into the outlet makes it a bit warm, while on others, it doesn't. Are there worse consequences than wasting energy to power up that green LED indicator on the adapter, whether it be an adapter for an external hard drive, phone, USB charging, laptop, etc.?

 

[Someone Somewhere]

No issue. Possibly slight energy wastage, but should be negligible.

Only danger is that if the prongs are uninsulated (as is the case with US and Indian plugs, but not most others), it's more targets for things to fall between the plug and socket and potentially cause a fire.