Brock is right. And you miss my point almost entirely.
You seem to think that evaluation is about deciding what to praise or condemn in new forms of communication based on pre-existing standards derived from previous forms of artistic production.
But when a friend sends you a letter, do you go through it applying a forensic literary standards? Do you give a 15 minute lecture on style and presentation when someone calls you on the phone? I don't think so. You enjoy the fact that your friend has sent you a letter or called you. And if you do the former, you probably don't get many letters or telephone calls from friends anymore!
The trick, as you put it, is not just to divide everything in the world, into black and white / good and bad. There is in fact far more than one trick.
The first trick is to understand what people are doing when they blog. Only some people are doing things to which you can apply artistic / literary critical standards. Most people are using this form of communication for things that are everyday, mundane, ordinary. There is no point in trying to think you can smugly (and rather illiterately) condemn these as 'shite.' In other words you have to understand communication before you can even attempt 'criticism'.
The next trick, for those blogs that do aim at something that pretends to more than communication with friends and collegues, is to develop standards appropriate to the medium you are evaluating. Not every medium is the same or has the same standards.
And so on...
And I suggest that your barrel metaphor is inappropriate. The Internet is not like a barrel (or a pipe or a highway come to that). The only thing that obscures what you want to see is a lack of effort in finding it. Nobody forces you to look at blogs you don't want to see. And there is, incidentally, more 'good' stuff accessible to more people now because of the Internet, whatever you evaluate as 'good'.
And in the meantime, whilst you blunder around in this new and unknown part of town, muttering and cursing at the terrible proles all around you, the proles are getting on communicating, learning, having fun in ways that were not open to them in previous decades or centuries, whether you think that what they are doing is artistically worthy or not.
That, my friend, is progress.