and what will a normal user do with that text file?

We find it much more effective to have an API that other people (like you) can use to write an exporter to whatever other service they wish.

Maybe you should just write a Posterous exporter using our API, instead of complaining. Just let me know if you need any help!

thanks

Because what are you going to import that file into? Everything needs a custom import format. Making the API available makes it easy for someone to write something that exports to the format needed. Do you think Posterous should host a different file that allows easy importing for all of its competitors? If the competitors care, they can make a tool that imports into the format they desire. Likewise, if a user just wants a text file of their contributions, they are free to obtain one. Someone could write these tools and publish them, but it's a little over the top to expect Posterous to write an exporter for everyone else's custom formats.