I don't really black list any businesses for political reasons, only for ones that I've had a really bad experience with.
#1 in my list is the local "Green Mountain Energy" company. Those people should all be lined up, and arrested for harassment. They come to my door. They sit in front of supermarkets, and their sales pitch is that I am gleefully and intentionally destroying the earth because I am not using green energy. One of them I told "If you do not get off my property right now I am going to call the police" after I closed the door on him and he rang my doorbell repeatedly. Those guys are crooks.
I also have had 1-2 instances where a debt collector has called me in error. I have no negative credit marks in my life. It's clearly and obviously an error. I give them one single warning, and will sue them if they attempt to contact me again.
I also usually do not do business with places that attempt to swindle me - Time warner cable did that, but they ended up giving me three free months of service as a result but I'm still gone the moment there is some competition here. I was setup for Autopay, and for some reason they decided to not take the money for two months in a row and started sending me disconnection notices, threatening letters, etc. Multiple calls, was never handled. They told me "Let's just make a payment over the phone" and I said no, fucking take it out autopay, you have my payment info assholes, don't tell me I'm not paying you.
Shit like walmart, apple, etc.. really nothing against any of them /shrug. I don't shop there much though, but shit.. sometimes walmart is just cheaper so why not.