It could be that they have a large enough allocation that they can keep doing this for some time to come. However, if they do start running up against their limits, then they are going to have to figure out how to reallocate and possibly even claw back those giveaways. I don't envy them, because even a low monthly charge per IP is going to cause bad feelings amongst customers who formerly got addresses for free.
What is the company, and are you otherwise happy with their service?
Softlayer, and yeah, they're great (at least on their dedicated hardware, not sure about their cloud services).