Technology of CableCARD; How long it’s been around? Why’s it important?
For the full nitty gritty details of CableCARD check out the Wikipedia entry which is fairly thorough. At a higher level, the technology was developed to protect consumers from being forced into having to rent set top boxes (STB) at increasing fees from cable companies (or MSOs) without an alternative. From a home theater PC (HTPC) perspective, it meant the ability to natively tune high definition programming from a cable provider (previously the options were only analog cable, or digital over the air broadcasts).
Originally, the exposure for HTPCs was minimal as there was a single tuner from ATI which required special Windows Vista activation from only a few OEM PC manufacturers; so if you wanted to have CableCARD it required purchasing an entire PC, leaving DIYers out. When Windows 7 was introduced, this requirement was removed and any customers were allowed to purchase ATI tuners and activate them. Until recently, CableCARD recordings were subject to fairly restrictive DRM, so even after the OEM requirements were relaxed, the technology was not viable for enthusiasts who wanted to placeshift the recordings.