Exporting data is lovely, but can we redirect our permalinks?

So, once I have my exported data I'll be able to import it into Tumblr. That's well and good, but all my previous content linking to Pownce URLs will be broken.

Even with the app taken away, setting pownce.com/benward/* to redirect to a path under the user's own domain would let me set up redirects to wherever my content ends up. I'm not suggesting you support the URL schemes of other services, that would be nuts, just the ability for users to throw all their links at one end-point and resolve them in their own way.

Obviously this goes a little further than just exporting content, but surely Six Apart, what with blogging being their game, would appreciate that reliable, stable URLs (some kind of hypothetical ‘permanent’ link, if you like) are a cornerstone of web publishing.