Hmm, I think that those URLs are still different resources; one is 'the current post' and the other is 'the post named "Why I love REST"'. I would do a 302 from the latter to the former.
I don't have a 'problem' with it, this is just conceptual talk. But I'd still do it for SEO reasons.
If Google fetched /blog/current as containing the "Why I love REST" post and showed it to me, and the when I clicked the link I got "Why I think turtles are awesome", I'd be annoyed. A 302 fixes that in a more clean way than entries in robots.txt or similar tricks.
EDIT: Apparently Google messes that up and often associates the content with the source URL and not the destination URL. Disregard the previous paragraph.