A friend was laid off from one of the 'big' banks. They were quick to point out to her that she'd signed a non-compete when they acquired the bank she was working for previously.
She had a job offer from another bank, but they weren't willing to hire her until this was resolved. She had a lawyer friend write a letter, pointing out the obvious - they laid her off, but didn't want her to work anywhere else either! The 'big bank' backed off quite quickly.
I can see the reasoning for the clause if someone leaves voluntarily, although that would certainly hurt most small to medium size town banks. They hire people from other banks to get their customers!
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Opinions my own.