I know people who have decided to not have cable in the house and rely on the internet for their entertainment and news. It's an idea that has intrigues me for some time.
After thinking of the subject a bit, I think i could live without cable. First this relies on getting a powerful internet connection. That's in general not a huge problem. I would also need an over the air antenna for local television, as well as the subchannels the networks have now. Beyond that is where the internet really gets important. I could use a PC for the internet stuff, but also use a streaming box like the Roku line of boxes for it, or both.
Most of my entertainment would come from subscription services like Netflix, Amazon Prime, and other streaming sites. I personally would also go to my favorite sites that now create video content and complete shows. One thing that I hope becomes more prevalent is cable channels offering subscriptions for online viewing. HBO sort of does that, but not where many hope it gets in the future.
One thing that has been an issue is live sports. I would probably subscribe to league packages like the MLS or NHL. I wouldn't get the local teams games but I would get some sports. Also the UFC offers their pay per view events online, so I can order them online. So it's doable, and looking at what it would cost, it would be cheaper than the cable bill I have now.