There's nothing 'new' in bondage..In the 60's after the first flourish of hiring ,nearly straight from school,BOAC/BEA found that after 3years the guys were leaving the scene..So BA required the candidates to 'stay' for awhile to cover the cost of investment(training)..Today a lot of Co's ,in view of the training expense($20-30K)are expecting the same return for their investment..Westjet doesn't follow this pattern,as far as I know.(they seemed affronted when applicants 'offer' the 2/3 year stint).
At the moment the only people with no strings attatched are the 'endorsed' applicants who save the Co'training..I believe this to be an Industry'Norm'
Some examples of bondage are 1 year for the 727,2 years required for the 757, and 3 years for the Airbus types...