You’re right that "walking off the land did happen". Although the feudal system legally bound serfs to the land, there were ways for individuals to escape this bondage. For instance, a serf who lived in a town for a year and a day without being reclaimed by their lord could often gain their freedom. These people, known as 'villeins' in some records, were essentially free peasants who had successfully left their lord's domain.

How does this compare to employment bonds of today?

At least I know of likes of Infy, TCS etc doing this (in the home country) — making freshers sign bonds for 2-3 years and if you want to leave within that period the only way is to pay a good amount irrespective of whether you didn’t receive a salary raise or didn’t get the opportunities which were good good for you. If you don’t pay the bond — they won’t usually drag you to a court (they send legal notices for sure) but they will also not issue you an experience certificate.