QAM is the method cable companies use send their digital signals over the wire. The 2009 change-over only mandates that over-the-air broadcasts have to be digital, this is the ATSC standard.  
In other words, cable companies may still use analog signals after 2009, though they are being phased out for bandwidth issues. Also the QAM tuners in these cards will only be able to pickup digital channels that are not encrypted. By federal law, the cable companies must broadcast those stations that are freely available over the airwaves in an unencrypted format. This means you're guaranteed to get your local network stations via a QAM tuner
Here's the kicker, you may or may not get other stations via a QAM tuner. For me, Comcast-Atlanta gives me all my locals via QAM (as they have to) and home shopping network stations for some reason. However, things like Discovery and History channel are on encrypted QAM. So no matter what, I need a cable box for these.