NetZero, best known for its low-cost dial-up offerings, is moving into the mobile internet game. The company has just announced a 4G service for mobile devices. Users can select from five mobile plans that range from $49.95 a month (for 4GB of data) to completely free. That free option isn't ad-supported like NetZero's dial-up, but it does come with some caveats. First of all, you'll need to spend $49.95 for a laptop stick or $99.95 for a hotspot that connects to up to eight tablets, laptops, or other devices. You'll also be limited to 200MB of data — as with all NetZero plans, service cuts off after you reach your quota unless you purchase "top-ups" or upgrade to a different plan. After twelve months, you'll be required to upgrade to a paid plan to keep using the service, and anyone who's already upgraded won't be able to go back to the free option.

The announcement doesn't specify what kind of 4G network it uses, but Engadget has discovered that it runs on Clearwire's WiMAX service; they got download speeds between 363Kbps and 4.7Mbps on the highest-speed option. That's significantly slower and more variable than AT&T or Verizon's 4G LTE networks, and although coverage is available in most major cities, it may be spotty. However, the lower-cost plans seriously undercut the competition: the $9.95 500MB plan, for instance, is about $5 less than AT&T's cheapest LTE tablet option and gives you twice as much data. As you scale up, the service becomes less economical, especially since you won't be getting the benefit of a faster LTE network. WiMAX isn't exactly popular with carriers, and even Clearwire is focusing on setting up its LTE network, but it looks like it's letting NetZero make use of that WiMAX capacity while trying to transition.