MongoDB is awesome. (Edit: not so fast)
Link posted on January 08, 2010.
"...as writes occur old data will start migrating to other shards."
Thanks Adam for pointing this out.
We recently started using MongoDB at work and, I have to say, it's been an absolute dream so far.
Update: This keeps coming back to haunt me, often in humorous situations. Want to know why? Read Adam's dissection of our recent history.