[gedrap]

Well, relatively speaking Postgre might have lower adoption than MySQL, although I am not too sure about it. However, if you look at the absolute numbers, Postgre has huge adoption, even if it is smaller than MySQL's. So it doesn't really matter as chances are, you will able to find an experienced developer. Can't say the same about HBase, etc since there are significantly fewer projects requiring it compared to MySQL/Postgre.