I think Scoble has run off into a niche, and doesn't realize it yet. Witness this:
But there’s a bigger trend I’m seeing: people who used to enjoy blogging their lives are now moving to Twitter. Andrew Parker punctuates that trend with a post “Twitter is ruining my blogging.” I find that to be the case too and when I talked about this on Twitter a raft of people chimed in and agreed that they are blogging a lot less now that Twitter is here.
It really depends on what your intent is. If all you are doing is keeping up with friends/family/peers, then sure - things like Twitter are probably good enough. If you aren't conveying a lot of real information, then 140 words will do it. If, on the other hand, you're trying to reach an audience (without regard to the size of said audience) with involved communication, then tweets just aren't going to cut it.
To take a simple example: look at the kind of thing Tim Bray posts, especially his recent exploratory series on various languages. Would that be useful in tiny 140 word chunks? I think not. It's also going to a narrowcast audience of software developers - and only a subset of those to boot. Those posts are highly interesting to that audience, but not outside it. What Scoble has done is to fall into the forest of "cool kid A-listers", and he's missing the many, many trees that are outside of his clearing.
There are tons of things going on outside of all of our interest spaces - that doesn't make them less relevant. Just because 140 characters does it for the "hip crowd" doesn't mean that it does it for the rest of us :)
web, social media