They give them away on Twitter you don't have to bug them at all. They post a message like "retweet this message to get a beta key, first 100 retweet gets it" and if you were quick enough and saw the message and managed to retweet it they will send you the key.
If you've missed out on it then you can try and message them to see if there are more keys available and what not. I just retweeted their message and 2 minutes later I got my beta key. It took literally 3 minutes and 2 mouse clicks.