O2 are encouraging you to sign up for spam tweets. The above promoted tweet might seem innocuous enough. Chance to win a super new HTC One M8. Good stuff.
However buyer beware. Once signed up I can't see how there can be an unsubscribe mechanism. O2 are hardly going to waste some of their 140 characters with a message on how to unsubscribe. Unless it's basically a simple unfollow. It's not clear. I'm not going to follow the link on the off chance of finding out.
There is also a basic problem with this whole concept. People don't regularly look for mobile deals and offers. They sign up for a contract and then forget it until the 18 or 24 months is up and then they look again. Am I wrong?
The way to avoid all this is to ignore the tweet.
PS Does win "an HTC" sound right? Win "a HTC" surely.