Florida law requires that sweepstakes sponsors must post a surety bond or establish a trust account for the value of the prizes being offered. Many sponsors cannot or will not comply with these requirements.
It's also a violation of Florida statutes to require a payment, entry fee, or proof of purchase to enter a sweepstakes. Since you normally have to pay to access the internet, Florida considers this a cost. Unless the sponsor offers an alternate means of entry (toll-free phone-in or mail-in entry), the sweepstakes would be void in Florida.