If you decide that you don't want your data stored on SimpleText.ws, it's easy to move on. The site’s code is open source, you can host it on your own server, and there’s a public API for getting your data out.
The server code is open source. The Google Web Toolkit based client code is also open source. Please take a look. If you notice something that I could do better let me know and I'll incorporate your change into the next release.
You can host the code using any server that conforms to the Google App Engine environment. Server options include:
SimpleText.ws has a public API so that other applications can sync with your data. The public API uses Google for authentication, JSON for data formatting, and has a RESTful design. The API is demonstrated and documented by this python client library.