amok: Edit - so the only thing this system stops is random giveaway and a reason to buy dozens of 1 cent bundles. I think it makes lots of sense. The bundles are just no longer trade-able in broken up bits.
Kurina: It stops you from giving them to friends and distant relatives. No matter how well I may know somebody, I'm also not going to be sharing my Steam account information or expecting others to share it with me so that I can give them a game. Not to mention, you technically shouldn't be doing that anyway as it could cause account problems and quite a few headaches dealing with support if too many people are seen accessing it, friends or not.
Also, how does it stop people from buying 1 cent bundles? I think that would increase for DRM free bundles. As far as I can tell, this will only increase the amount of people paying the absolute minimum since they are no longer getting the spare keys they would like to share, especially for products they already own. The comments on other forums especially seem to be suggesting this behavior in the future.
You may still buy a bundle for 1 cent, but there is no much more point getting 2 bundles for 1 cent....
And yes, I do not feel sorry that HB now felt the need to enforce the rules they kindly asked you to obey before. I do not think this would have been a problem if you only gave a away keys to 'distant relatives', but only in the fashion that we are all related to a 7 degrees of separation... At least this puts a stopper to the argument "if humble did not want us to do this, they would not let us".
I just increased my payment by $10 over what I normally pay encourage HB to continue with this system. It also made redeeming keys a doodle :)
edit- or to put it in a different light - if people (I am not saying you did) did not abuse the system as they did, you would now still be able to give keys to family. However, we both know that most of the keys given away or traded did not exactly go to family...