We've been looking into it. I'd really like to get that done, but it's a non-trivial undertaking, and Meteor's DB APIs are still in flux.

I'll see what we can do to accelerate this -- possibly by enticing the community to pick this up.

Please consider this encouragement to do so, because MongoDB is an instant interest killer for Meteor right now. I just don't trust MongoDB at all.

If you post what needs done in detail, someone will surely pick it up. I'd certainly take a look and see if it was within my capabilities.