All United States and Europe players with a Battle.net account who enabled the Hearthstone Opt-in option have a good chance to be among those Blizzard Entertainment just invited to test Hearthstone Beta. Check out your email in the next 24-48 hours and double-check if you got one.
Yong Woo tweeted both US and EU Opt-in players were invited to test Hearthstone, and more waves of invites are coming in the near future. Additionally, there was a record of concurrency of players flooding the servers.
Yong Woo clarified that by US (United States servers) — he means players from South East Asia (SEA), Oceania: Australia/New Zealand (ANZ), North America, Latin America were invited yesterday, and many more will be invited more often in waves. This is the largest batches of invites ever going in Hearthstone.
I know you are very excited, but always precaution first and foremost. Beware of scams. Do not click on links blindly before checking the URL destination carefully.
Don’t forget to visit your Battle.net account page in case the Hearthstone beta has been enabled on your game list. Good luck everyone! See you at an Inn near you, matey!