Let's just say they'll find consideration where they can, even if it wouldn't constitute consideration is a different kind of case. For example I found more than one case that enforced a pledge when the donor knew it was part of a project contributed to by other donors. The consideration wasn't something given by the donnee, but the promises of the other donors to make gifts to the same project.
It's not normal consideration because the donnee doesn't give anything and the donor doesn't receive anything. But the other donors will presumably be disappointed if someone's pledge is not satisfied. That's all that's required. Sort of like saying that a contract is enforceable simply because there is a third party beneficiary, even if there is no consideration.
Stu