Big data, small code

Building a big data driven web application used to be a big thing. Relational databases, links tables, complicated queries and stored procedures...
Java containers, cache management, state - Big architecture, costing a lot of money, setup and development time.
Scaling also used to be a big thing. Databases needed to scale. Web servers needed to be synchronized. Whenever state or caching was applied, data integrity was a big, big issue.

With new servers like node.js and databases like mongodb, the web stack just got a whole lot simpler.
No need for complicated tables, queries.
IO is faster, without the need for object translations from tables to xmls to jsons or whatever.
And - More important - Indexing, multiple indexing and complex queries are supported as well.

Programming is also much, much simpler. Using dynamic language like javascript is much simpler than using Java. The whole setup is simple - Actually, these servers are extending javascript to be a native language, rather than living inside the browser sandbox. That way, your whole web application is written in one language.

Connectivity modules with other services (amazon, azure, mysql etc.) are available, and expanding rapidly.

My suggestion - Give it a shot in your next web application. If you like javascript like I do, this might be the smartest move you've done.

Edit: (Thanks to @lightpriest for pointing that out): Like all software solutions, you also need to make sure that this solution serves your problem better than 'old' web stack solutions. Read the other side here.