Is The Shoe Carnival Sweepstakes Legal?

I know there are all kinds of rules about sweepstakes. That companies have to allow people to NOT purchase items to enter, etc. And I also know it's not about the sweepstakes: it's about creating a mailing list. I just wonder if Shoe Carnival's new online gimmick is totally legal.

You earn extra minutes for each person you refer to sign up, making it kind of a pyramid. The point of the game is to be quick, and you'll get your own text message that much quicker if you get a bunch of your friends to sign up. However, all those people are now below you, so they can only pass you in quickness if they get some of their social media buddies to sign up, and those folks also drop to the bottom, etc.

It's a pyramid sweepstakes, rewarding those who bother their friends. It will probably get all kinds of new email addresses to the Shoe Carnival list, and I'm sure it's marketing gold. I've just never seen an online sweepstakes done like this, so I have to wonder at the legality. I know Linkedin was busted for the way it pursued friend's emails from members, and I can't see that this is any better. Plus, I always thought that a sweepstakes was based on chance. This one's based on number of friends and how much free time people give themselves while at work.