Ranking for signal to noise ratio
A whisper in a quiet room is all you need. There's so little noise, so few distractions, that the energy of the whisper is enough to make a dent.
On the other hand, it's basically impossible to have a conversation (at any volume) in a nightclub.
Signal to noise ratio is a measurement of the relationship between the stuff you want to hear and the stuff you don't. And here's the thing: Twitter and email and Facebook all have a bad ratio, and it's getting worse.
The clickthrough rates on tweets is getting closer and closer to zero. Not because there aren't links worth clicking on, but because there's so much junk you don't have the attention or time to sort it all out.
Spam (and worse, spamlike messages from organizations and people that ought to treasure your attention and permission) are turning a medium (email) that used to be incredibly rich into one that's becoming very noisy as well.
And you really can't do much to fix these media and still use them the way you're used to using them.
The alternative, which is well worth it, is to find new channels you can trust. An RSS feed with only bloggers who respect your time. Relentless editing of who you follow and who you listen to and what gets on the top of the pile.
Until you remove the noise, you're going to miss a lot of signal.