And guess what? We've already implemented it on this blog for louisgray.com.
Set up your API key on both services...
As the Disqus blog points out, an enterprising Disqus community member, Carter Rabasa, put together a quick application on Google's App Engine, called FF2Disqus. By entering your API key for both Disqus and FriendFeed, assuming you use both services, the tool will check your blog posts on FriendFeed and pull in FriendFeed comments to your site, or send Disqus comments to FriendFeed.
The result spits out the copied over comments...
There's no installation process, no scripting and no code. Just run it once and you're good to go.
You can choose to make the connection unidirectional, from either FriendFeed to your blog, or the other way, or to have full synchronization. I enabled it to copy over FriendFeed comments to my site, effectively replacing the Yahoo! Pipes solution I'd asked Pat Hawks to create last June.
The result is pretty straight forward. If there is a comment on FriendFeed, it is displayed by Disqus on my site, in the order it was posted, and the author's ID links to their FriendFeed user profile. Now, what the solution doesn't do is crawl FriendFeed and find all comments on all reshares or tweets of your blog. It just gets the one main entry, which I think is good enough. It also is bound to have some disjointed entries as conversations are smashed together, but it should be a good experiment to see how the two could merge.
If you're a FriendFeed user and a Disqus-enabled blogger, you should really check out FF2Disqus at https://ff2disqus.appspot.com/.