The Electronic Sports League set up a spamming competition for 800 free gold and 1 day of premium bonus codes HERE.
You get extra chances by connecting your Twitter, FB and Google accounts and subscribing to different pages, channels and accounts.
While it is annoying it is official and you have an actual chance to win something. The payout is not immediate. There is a draw going on every day and you will be notified via your e-mail if you win (so if you use your FB account, you will be notified via the e-mail connected to that account).