You're externalizing blame.
If you have a problem with 'hoppers' have you looked into why you're failing to retain people?
Small companies are especially bad for that: fewer employees means fewer paths for personal/professional advancement: there's nowhere 'up' to move, and wearing a half-dozen hats might seem like variety at first, but you'll be wearing those same hats forever. It's too bad that they have less room to take the hits from people leaving and new people coming up to speed, but it's also unreasonable to expect people to stick around past the point they gain anything from the exchange. People *should* be moving on when they feel they're stagnating.