Having directly hired and trained a few people under me, I understand how unbelievably hard it is. While from a management/HR perspective, it's always the feeling that throwing more bodies at a problem will fix it. But hiring good developers, and MUCH more importantly, training them properly and delegating tasks accordingly, is to me, the lifeblood of any tech company.

As for the fear of other opportunities - that's a good thing. It drives you to create a better work environment, offer them more. It's not the fear of them leaving, it's the challenge of "how can I do better?"