This method which is used by freebiejeebies to get you free gifts is similar to referral incentive scheme used by Sky digital, where they give customers £50 Marks and Spencer vouchers if the refer people to join SKY. The differences with method used by Freebiejeebies are, you don't have to sign up to any expensive contract services and you get a free gift that you actually want.
Who benefits?
Everyone benefits from this scheme (You , the advertisers and the freebies site). Here is an illustration to show how everyone benefits.
At the end everyone is happy. You get your free gadget, the freebie company makes a profit from commissions from the advertiser, and the advertiser gains a potential new customer who might continue after they complete a trial of their products/services.