I recommend anyone I feel is a good pilot, and will be a good crew member to work with. If not I don't recommend them. I don't really have a dog in the fight as to whether they leave within a year or not. Nothing in my letter suggests they will or will not stay.
JetBlue is a business. It is up to the interviewer to decide if the person is a flight risk or not. No pun intended. Personally, I like it here and have no intention of leaving. However, I live in base, and driving to work is priceless. I have young children and value the time I get as a result of living in base over commuting. If I were a commuter anyway I might feel different, and would no feel bad about leaving.