I had to look that up. I thought that app.net (despite the name) was a twitter clone except that you could write somewhat bigger messages and had to pay for it.

Searched for it on ddg and here is what the excerpt from Wikipedia says: "App.net was an ad-free online social networking service and microblogging service which enabled its users to write messages of up to 256 characters."

Turns out that they did a lot of stuff later that I would have liked but by then I was probably using WhatsApp.

A cautionary tale for sure.

My thought is that something new would need to not replicate the UX of existing social software, but would need to think of better alternatives. Competing with existing giants on their own terms, but with a different business model, is a hard sell, probably too hard.