I can see why's that would be frustrating, but my employees are not "mine" - so they are free to go at any time and hence, I need to treat them well.

If an employee is seduced by an offer that doesn't work out - they can (and have) come back and can bring back what they learned.

One of the thing that I learned from such exits an re-entryies is that money is not always the best motivator - I used to run really lean to have a high payroll. Now I run lean to provide a good work environment - I can now fire bad companies that don't respect my employees.