In my area, Time Warner has a $15/month internet plan that offers 3MB down/1MB up. Most Mustachians are cable cord-cutters and rely on some type of video streaming service for entertainment which pushes the limits of this 3MB download speed. It is entirely possible to watch streaming HD content, without buffering interruptions, on a 3MB connection though - you just have to set up QoS (Quality of Service) on your router.
What QoS does is allocates bandwidth priority to your streaming devices - your Roku, your Playstation 3, Amazon Fire, whatever network device you use to stream video. Those devices will get priority access to your bandwidth, typically 95% or more. This way whenever you're streaming a video and your phone wants to update Facebook, it doesn't drag down half of your bandwidth and cause the video to skip. Instead, your phone would be throttled to a low speed.
QoS is available on many routers on the market today, as well as on 3rd party firmware such as DD-WRT. I would highly recommend using it and not paying for unnecessary bandwidth.