If you're not familiar with Aereo, it's a cheap, seemingly too-good-to-be-true streaming television service that piggybacks television broadcasts on network streams, letting you "borrow" the telecast with a dime-sized antenna. It's a very cool innovation, but if it sounds shady...it's because it kind of is. The DoJ seems to thinks so to, believing that Aereo is re-transmitting broadcaster's content to the public – not unlike a cable company – and is therefore in violation of Federal copyright law. We'll all know more on April 22 (Earth Day!) when oral arguments are held.
TLDR: If you're one of the few urban areas (like Denver) that have the benefit of Aereo service, you might be losing it, and in short order. See the image below for a brief overview of Aereo, and read the rest of the article here.