Too good to be true?

Recently I noticed Imageshack, which is a free photo hosting service. It seems too good to be true—for no charge at all they'll give me unlimited storage space, plus auto-generation of galleries and thumbnails—but it also seems to be real. I'm using it for today's image, and if nothing goes wrong I'll carry on doing this in future, because in the long run it will save me money if I don't have to buy more server space.

If you use or have used this service, can you tell me if there is a catch?