I despise signing bonuses. Look at the regionals in the States. They'd rather pay signing bonuses when times are good and it's hard to find enough pilots willing to work for crappy money than raising the general wages because you'll be stuck with them once the industry hits rockbottom again.
Good for the company, bad for the crews.
As mentioned before... a good employer won't have to pay "loyalty bonuses" because pilots will actually want to work there and stick around.