I don't know about HBO, but Netflix has spent a lot of effort building quite sophisticated methods for detecting and blocking people trying to connect via VPN
In my experience, it varies... I had one VPN service start to get blocked consistently, so I switched to another, and that's been going smoothly for two years. And I'm sure Netflix can put cookies on my machine and know what's up... I'll be in Japan and then minutes later I'm in the US again with the same computer.
I guess this is a requirement from the content owners.
It's a requirement to drive people towards torrents? Why do they keep making it hard to us to pay them for the content we want?