So many platforms can be viewed as note-taking tools with varying degrees of certain qualities.

People take notes on Twitter, using threads to document observations about visiting a city, UI gripes, or taking public notes in a conference in ways that others can see and share and add too.

But Are.na functions the same way! You can collect things in threads (channels), people can leave comments, it grows over time, etc.

Same with Tumblr! There's that old meme that you can just find <anything>.tumblr.com. Tumblr's comment and publication structure is odd, but it's there!

What's the difference between these systems? Why do they attract such different audiences and kinds of notes?

I suppose what this reveals is that the web is actually one of the best note-taking tools out there. URLs, hyperlinks, embeds… it's all the structures needed to take good notes.