MongoDB has good drivers for Node (as for most other languages) but also a fully-featured ORM that can save time in these kind of projects: mongoosejs.com
MongoDB also ships with a JS runtime so you can run map/reduce calls written in JavaScript entirely DB-side, as well as other goodies.
So it's fair to say that the language that makes the most sense when using MongoDB is JavaScript, even if that wouldn't be enough IMHO to justify using Node for a project.
I never understood why you needed ORM for a database that stores objects... Validation is the only problem it helps in but there are other ways of doing that.
MongoDB also ships with a JS runtime so you can run map/reduce calls written in JavaScript entirely DB-side, as well as other goodies.
So it's fair to say that the language that makes the most sense when using MongoDB is JavaScript, even if that wouldn't be enough IMHO to justify using Node for a project.