Over in this post, Brian Aker talks about a popular social networking application (Foursquare), which recently moved off a classical durable transactional store (Postgres) and onto a new-fangled NoSQL system (10gen MongoDB), and how MongoDB's very poor durability is negatively impacting the end user experience (e.g. Foursquare keeps losing a days activity stream history).
I posted this comment:
One of the things I took away from NoSQL Live in Boston is that the standard "MySQL master/slave with replication" configuration is even worse than most of the NoSQL solutions out there already, not even having an "eventual consistancy" guarantee, instead having, at best, "wishful consistancy".
I sometimes quip that MySQL 3.11 became popular a decade ago because it fit very well to quickly and poorly written PHP3 apps. MongoDB may be the modern version of that, fitting very well to quickly and poorly written Ruby apps.
But I fear that because that because 10gen has VC mindshare over other technologically better document stores and other NoSQL stores, it might win on the "worse is better" principle.