Kassem wroteBut have you ever used RavenDB or any of the other alternatives? In case you did, do you think it's a better alternative to relational databases?
Not in production yet, I've dabbled with it couch (through the web admin + curl) and with mongo (through the .net mongo mapper) as a personal research and I've found it quite nice.
Document based databases are not alternative to relational databases but complimentary. As soon as complex relationships get in place, document based databases fail miserably. On the other hand, you would notice that giants are using mongodb for example to solve certain issues, like Twitter with their URL shortening history and i think facebook uses it as well but i don't recall where exactly.
I will however, be using one of them to solve a problem with a project at work, that deals with ever-changing domain models.
P.S.: Sorry Kassem, i edited your post by mistake. I restored it back to its original content.