Another example of 10gen winning a highly technical market not through technical prowess but with superior marketing. I'd rather not argue whether MongoDB is better than other NoSQL solutions or RDBMS. But I do applaud their effort to get developers up and running with MongoDB quickly and easily, especially in contrast to $1000+ support/training for MySQL and Postgres.
10gen really nailed this; the meetup groups, customer support, drivers, docs and ability to get going are all awesome compared to most products, let alone the other databases competing with them.