Sinatra is awesome. I used it as backend api for a JavascriptMVC¹ application, and it worked great. It's just impressive how productive you can become with a good dsl that covers your needs.

¹http://javascriptmvc.com/

thanks to everyone who continues to make Sinatra better.

I think Sinatra is the optimal web framework for most startups.

Could someone give a good use case for streaming?

Twitter Streaming API: https://dev.twitter.com/docs/streaming-api

HTTP Based Pub-Sub: http://faye.jcoglan.com

Implementing HTTP long polling, which can be used to implement for example instant messaging. At redbet.com we used streaming in thin to implement the odds updates in our live betting.

The "Campfire streaming api"[1] would be a good example.

[1]: http://developer.37signals.com/campfire/streaming