It's incredibly common in Europe as well, yes, but usually the numbers just about work out with some no-shows and reshuffling people across classes.

Also, the ones they do bump off are the standbys and reduced fare, which is why you don't often hear about fully paying passengers being forced to take another flight - and in any case, if they're still over capacity, the promises of free upgrades and money mostly result in enough volunteers to prevent that from happening.

I'm not sure about any differences in US regulations vs EU regulations for this issue though.