[Frost1x]

Voluntarily doesn't disqualify something from being slavery. Historically, if you look at indentured servitude you'll see this very trend and indentured servitude is classified as a form of slavery (albeit, arguably, not as bad).

Interestingly, if you want to look at a modern parallel, it's not too far off from how H1Bs are used. There are of course more modern rights that allow individuals to quickly terminate these responsibilities but essentially contracts hold needs (income, assets) and desires (citizenship) hostage as the bargaining mechanisms, not too far from what many indentured servants entered into. To be fair, working conditions and treatment have also of course increased drastically.