At a net cost of five (4 + card), you effectively discount the printed cost of two allies down to zero. If you get two three-cost allies into play, you're up one resource, making this effectively The Power of Leadership; if you get two four-cost allies into play, you're up three resources, which is completely nuts. If it helps someone spend resources they didn't otherwise have a use for, even better!
Best in multiplayer, so you have help to pay for it, and so it's more likely you'll have appropriate allies in someone's hand. Try using it with Regroup to make extra sure people have good allies in hand!
Note that the allies aren't actually being played, so Spider-Man doesn't get to blow up a side scheme, for instance.