Three basic forms of posting stuff on the internet:

1. The update: short, immediate. Useful for conversational missives. Twitter, Facebook et al.
2. The name to be decided: a thought, observation or reaction that requires more than 140 characters. Tumblr, Posterous this theme et al.
3. The article. Longer form text that analyses or discusses. The traditional blog post (see my blog).

Which to use? Depends on mood, style of writing, time and a thousand other factors. Online formats are proliferating more than in print, probably due to the democratic, informal nature of the medium.

It’s a good thing, by the way. I err to #2.