Are Dota 2 Giveaways banned on here?

Yep.

Reason: Massive flood of giveaways knowing that you can get it for free if you do the survey.

You can sell them for 1p each in the steam marketplace if you wish?

Feel free to give them away on the forum, you just can't create normal giveaways for them.

Gift them to Dota 2 Dispenser.

Wall of Shame

They're so easy to get, they no longer have a gift value, so the DOTA2 option has been removed from the list (plus the site was getting thousands of them, and that's no fun for load times).

You could always have a forum giveaway though!