I tried to get some at work for when people travel and none of them had an earth. All our laptops have an earth connection.
We had 2 users visiting the US without a travel adapter so they went to Home Depot, bought a screwdriver and a 2 pin plug and nearly electrocuted themselves. I asked what they did with the earth and they said that the US doesnt have an earth so they cut it off. They also didnt think of the voltage difference. It is scary what people can cobble together
I took my time, I hurried up, The choice was mine, I didn't think enough
The ones I know are at least built in a manner you can only insert ungrounded plugs (i.e. use class II devices). Doesn't make them that much better though, trying to run a hairdryer plugged into a US power strip was the first and probably last time I tried to use such an adaptor. I've got plugs for the countries I'm most likely to travel to (French, Italian, UK) and should I decide to go somewhere else I'd try to get plugs beforehand and make up my own extension cord.