Dave: The problem with remote "managed" servers is that sometimes you can't get to them when you need to.Local data is as important as local processing power, my point is about local long-term storage: while I do want to have a copy of everything here, I don't want to worry about it.
I think that the coolest feature of Radio is the fact that it automagically keeps a copy of every file I drop in the a local (www) folder on the server. It's a feature that a lot of users have have not even realized it's there and it's the main reason I keep using Radio: when I want to share a file I simply drop it in a folder. This can only be done by an application running on your computer.
But when it gets to blog data, Radio keeps the raw data in a local database and uploads on the server a rendered version of the page. If I loose my local database I will still have the rendered version but I won't be able to re-import it.
The solution is actually easy: move the rendering code back on the server and upload raw data instead of rendered pages.
Which I think is just what OPML does: it uploads an OPML file which is then rendered on the server. Theoretically I could rebuild a lost OPML install recovering data which has been uploaded on a safe server (but this takes us to synchronization-land, a place programmers usually tend to avoid ;-).
PS: also see what Cristian says about this.