Well, all queries are accessed through URLs. There are two types of queries: temp views and permanent views. You can use apache/nginx to redirect all query through URLs for temporary views. Permanent views are stored on the db. That way, your client can't execute arbitrary queries. Then, the client can only be limited to views/queries that the web dev set.

http://wiki.apache.org/couchdb/Nginx_As_a_Reverse_Proxy

Then as long as the client can keep its identification token secret from others, you can implement "user can only query their own blog entry"

I suggest you look into couchDB a bit further. CouchDB is a different beast altogether from relational databases. Therefore, the assumptions you make about what a database can and cannot do coming from a relational world doesn't always apply.