It is not quite a Ponzi scheme or chain letter, since (presumably) only one referrer could collect the bonus, but it might produce patterns where many people in one department follow the lead of the first one to migrate.
OTOH, if the bonus is linked to the starting salary, HR may now have an incentive to low-ball the start, and then increase to retain.
Cui bono?
Additionally, a 10% of annual compensation referral bonus is generous; even if it can only be collected once.
I could easily see people coming to expect these bonuses, starting to rely upon them to pay for their holiday shopping, etc, to the point where politics and drama could result.
Of course on paper, even one 10% referral bonus would be better than most existing ones, but people don't behave rationally about money, and we quickly get used to our "bonuses"...
The unintended consequences listed here are interesting as like any system, people will learn how to game it.