I don't know they aren't, but it's illegal. Large hedge funds are unlikely to be breaking the law, and I haven't seen any evidence that they are which wasn't based on a misunderstanding of the free float numbers.
Stock borrowing is very very commonly done and renewed per-day, in the vast majority of situations this works fine.
Stock borrowing is very very commonly done and renewed per-day, in the vast majority of situations this works fine.