One important thing to look at when discussing this topic is how much people in the world today use or view the different types of media in question. With the introduction of DVR'S, a lot of people don't even watch television commercials and advertisements any more. DVR's record your shows so that you can fast-forward through those obnoxious advertisements. What are the latest products out there? Who knows? I don't watch commercials! What movies are coming out soon? Don't know, because I fast-forward through the trailers. A lot of people have DVR's now, and that means that television advertising is losing a lot of viewers.
Compare that to facebook and twitter. Granted, a lot of people don't have facebook or twitter accounts, but when they do, I gurantee they are spending more time on those accounts than they are watching t.v. commercials, looking at magazines, or reading newspapers. Also, the scope of impact is much larger. Whereas television commercials, magazine ads and newspapers present information and influence product consumption, facebook and twitter influence a much larger portion of our thinking. We socially network through these sites, we form friendships and relationships. Those friendships and relationships affect most of our opinions about many, many different things. That holds a lot more power than a 2 minute blurb on why you should wear Old Spice deoderant; whereas that commercial impacts the choice of deoderants that you make, facebook and twitter can influence opinions on politics, religion, sports, morals, values, friendships, relationships, principles...the list goes on and on.
Those are just a couple thoughts to get you started, and I hope that they helped! Good luck!