Hotel desks and lamp based power outlets are as capable (roughly!) as wall outlets + a powerstrip. Your USB charger has an output of 20-40W, they are above 70% efficiency http://www.righto.com/2012/10/a-doze...-apple-is.html and so they need about 30-60W on the plug meaning less than 0.5A. Half an ampere is absolutely nothing. It's only the very special (I only met them in the UK) bathroom shaver outlets that *might* have a problem with them -- see http://blog.fosketts.net/2013/02/03/...trical-outlet/ here for these ones, 20-40W is typical. Look at it this way: the hotel desk / lamp base can take a laptop power brick. That's a 65-90-135W DC brick right there, far far beyond of what these puny USB chargers provide.

Ps. if you plug in a 10-20A hoover into one of these based on my post and the cable melts then you are responsible for the electric fire. Use your brain