You can access HBO Go via a Roku if you are a Cox customer or Time Warner Cable customer; two huge cable companies. This is a not an issue between Roku and HBO. For other devices (like my phone) HBO Go lists Comcast (Xfinity) as an option for verification. In other words, Comcast allows verification from that device. Why? Comcast's bread and butter is not in the mobile phone market.
It is the cable TV market (emphasis on TV - not computer or tablet or smartphone).
They are specifically denying Roku set top box activation. Cable boxes, which you lease from providers, are set top boxes of a type just like a Roku. But then so are modern Xboxes and Comcast allows that (although only after massive outcry from owners). Think about it. Does Comcast tell you what computer to buy when signing up for Internet access? No. Do you have to lease the modem they offer? No, you can buy your own. The one place they keep a firm grip is your TV. They may not tell you which set to buy but they pick and own the hardware between your TV and their service. The Roku also goes between your TV and (one) of their services. In fact, it circumvents the cable service and uses the Internet. That may be the nail on the head. Comcast does not want you going around cable access to get to your HBO. Beyond stupid. You still have to subscribe to HBO and in order to do that you still need a cable package. The reason they might care that you are not using the cable box? If I'm not using the box, I won't order additional content, you know that lucrative pay-per-view stuff, or I might order less.
I may be reaching here but I'm grasping for some form of logic to make sense of the denial on their part. I just want to watch True Blood and GoT on my nice, new HDTV. The biggest screen in the house. We will still fork over too much money each month for our limited storage, piece of crap DVR because my son's shows are there. They won't be losing an revenue from me. All the more reason it pisses me off the deny activation.
The Comcast rep at Best Buy tried to feed me some BS company line that Roku and HBO are working out content licensing issues. If that were true, Cox and Time Warner customers would be out of luck if they owned Rokus. Those customers are not. They are able to watch HBO Go on their nice big HDTVs while Comcast customers can only stare at the utterly useless HBO Go channel in their channel line up.
You know what is even better? In the same Best Buy with the Comcast kiosk that told me it was a Roku vs HBO thing, is a big end cap promotion for Roku. Do you know what is splattered all over the marketing? GAME OF THRONES. That's right an HBO original series you would ONLY be able to watch on your Roku if you are able to activate HBO Go. In my area, Comcast is pretty much it. If someone goes into that Best Buy and signs up for Comcast and then says, "sweet, a Roku and I can get my Game of Thrones on" they will get home and be sadly disappointed. I'm sure there is some fine, fine print about limited availability for HBO Go but like anyone is going see or read that.