Is your app pushing the limits of SQL databases?  Is there any reason to look at NoSQL other than the fact that it's 'cool'?  Currently all the NoSQL databases are very early adopter products, and each have their own strengths and weaknesses, so you'll have to choose a NoSQL database whose strengths match the area where a SQL database is failing you, and where the weaknesses aren't deal breakers.<p>Of course I'm biased, and tend to lean towards using SQL/relational databases...  FathomDB is all about trying to eliminate the pain points of running a (My)SQL database.  I feel a lot of the NoSQL marketing hype is picking on weaknesses of MySQL (rather than relational databases per-se), and so we're thinking about how to make MySQL better, and we don't think it's a good idea to abandon the relational model entirely.  After all, our industry started with NoSQL back in the 60s, and there were good reasons for adopting the relational model 30 years ago!