A few weeks ago, Apple took an important first step in making this a reality when it teamed with Alpine to bring a set of car stereos to market that allow listeners to tag songs for later download via the iTunes Music store.

I like this move, but it’s not that big of a breakthrough – after all, Shazam recently eclipsed 50 million users (who are primarily tagging when driving) and closed a round of funding from A-list VC firm Kleiner Perkins–putting them in a nice position to own the music discovery market.

The bigger opportunity – and one that has Google written all over it – lies in an easy way to tag commercials, talk show segments, news and other information while driving. This is underscored by the fact that most songs that get radio play these days are on the pop charts, are in regular circulation and can easily be found of iTunes with a click or two.

But, when you’re in your car, you usually don’t hear the same piece of information twice. News bits are regularly updated, ads are timed to optimize reach and frequency and conversations happen only once.

For marketers, giving consumers that are interested in content or promotional messages but have their hands tied when it comes to taking action, an integrated radio/Web tagging system could be just what it takes to make radio more actionable and most importantly, more measurable.

For terrestrial radio stations, this type of system creates new value for listeners and aligns radio with the important trends that have led to ad dollars moving to digital mediums.

And for everyone involved in the radio ecosystem – advertisers, stations and consumers – it combines the real-time nature of radio (which podcasting can’t deliver) with the direct response nature of the web and could help save this dying medium.

Here’s a prediction – not for 2010 – but for 2012 or beyond. Like Apple, Google will align with car stereo OEMs (or hybrid GPS/car stereo systems as they are doing with Google Earth and the upcoming Audi A8) and integrate tagging capabilities into their devices. In a few clicks, you’ll be able to “tag this segment” or “tag this ad.” These tags will then be queued locally on your stereo and eventually surfaced to iGoogle or some soon-to-be-launched dashboard that aggregates your tags from Gmail, Google Reader, Google Docs and the like.

Then, you’ll be able to listen to the content again using Google Voice (transcribed for reading via Gmail, of course) and with embedded calls to action (call this merchant, comment on this story, etc.), so that stations and their advertising partners extend the relationship with readers beyond drive time. Google could also roll out a “switch pitch” bidding system to allow advertisers to deliver offers and promotions against tagged content.

Right now, the infrastructure isn’t there to make it happen. But as Google rolls out more free wi-fi the US and as current connectivity solutions already in cars, including bluetooth, satellite radio, etc. bring the Web to our cars, it will be. And a new term, “driving the Web” will be coined.