NoSQL is good if you need flexibility in the data you store. So if you wanted to start collecting user's twitter handles, you could easily add that and then stop collecting them anytime. So some records would have twitter handles and some wouldn't. The table structure wouldn't have to change.

Also, MongoDB in particular has a geospatial data index. So if you were using location data and querying by location (e.g. what's nearby a user's location) that's a great feature. Not sure if other NoSQL solutions have that or if just Mongo.

I can only speak for myself. I’m unfamiliar with sql and don’t need complex queries. I am also not sure how to deal with sql injections and don’t want to spend time on figuring it out.

I also don’t have a clear picture of the structure of the database when I start a project . I want to have the flexibility of adding entries whenever I want.

I’m using mongodb now. I am aware it has issues, but its programming interface is convenient.