Okay, I'm going to do my best to explain this as I know it.
Yes, it's completely legit BUT the offer is only good to the person who's name is on the invitation. If it's addressed to your family, then anyone can get one. If it's your husband, only he can get it, etc. My DH got one and I had him get us one and then we got another one in the mail to our family and I then got my own. Once you use the card to make your first purchase, the gift card will be mailed out. We now have $400 in gift cards not counting what we've earned in rewards. We now use these cards for everything in order to obtain rewards. We received yet a third offer and I thought about cancelling my current card and re-applying but I'm not sure that would work. There is an invitation code on the offer that you must provide and they'll make sure the code matches the person's information on the invitation. You'll see other offers for a $50 credit, etc. but this is the best I've seen. I've no idea how it's decided who gets it BUT if you send a friend to the program where they get I believe $25 credit, you'll also get $25 gift card as a referral. Hope this helps. Don't forget the 10% off on disney merchandise with $50 purchase AND you get perks at the parks (free character picture, etc.). Hope this helped. We figure this just payed for probably half of our ticket costs for next year.