Just to clarify the above post by Smokie, a company cannot bond you for something it has not provided. If, for example, you turn up with a valid type rating and simply need an OPC or LPC to get back on line, a company can't then bond you for a type rating it hasn't provided- that is illegal.
On the other hand, if the company in question deems your ability or previous training to be inadequate, it may want to re-train you, and that is something they can obviously bond you for. The point is, they have to be able to point to an expenditure on their part in order to enforce a bond- which has to be reasonable.
Also, some companies bond for initial checks and/or LPC/OPC, annoying as this may be it doesn't usually represent a lot of cash.
Finally, I am very much against the practice of selling type ratings, or, for that matter, bonds. However, the practice is becoming more widespread, and what it really represents is an attempt to control costs and reduce training risk. This is a perfectly reasonable business practice and does not imply the operator is somehow "fly by night", and it also says precisely nothing about a companies cash situation- is Ryanair cash-strapped? Don't think so, and they make you pay for everything!!