True, it also states the person has no loyalty to their current employer if it means an extra $10k a year. This could be a red flag for some, or an opportunity. I am not in the programming business, so wonder what the turnover rate is at tech firms.
If they're unhappy, or need that extra $10k, let them go for it.
Or they can heavily encourage it, with vesting stock options, seniority based raises/promotions, etc.
Relying on "loyalty" to keep people when the employer has shown none (an employment contract that has penalties if you're laid off? Only for senior execs) is just a bad idea.