The rise of the chaoticians
Over the last decade, we have seen an increasingly jaundiced eye being turned to toward what I would call the library sciences. Foundational concepts like controlled vocabularies, taxonomies, data types, part/whole relationships, relational algebras etc. all require data modelling work up front. Often, they require a lot of work up front. The theory goes that the time spent up front on the information design will allow the rest of the project to proceed waterfall-style and will lead to systems that are optimal in terms of performance and accuracy.
There are a number of problems with this theory say the chaoticians. Firstly, you never know up front what the information model will need to be. Rather, you discover it as you go along (a world view that resonates with the agilists also). Secondly, it is no longer such a big deal to have an optimal model in terms of storage or performance. Who cares if a more chaotic model entails some extra processing or eats some more storage or creates some “false positives” in the results? An abundance of cheap processing power and storage density deals with the former and human nature deals with the latter. Look at a set of results from a search engine. Some are false positives. In fact, the majority of them may be false positives. The search "hits" are statistical in nature or, put another way, wrong. The chaoticians argue that it often makes more sense to deal with the statistical nature of the results than slave for years to find the perfect, normalized, relational model.
The chaotcians often point to the memo fields and blob storage layers in relational databases as evidence to support their cause. Over time, it is not unusual for memo fields to end up as repositories of very rich information in a relational database. Once out of the rigorously controlled, rigorously data-typed table/field structure, it is "in the database" but it effectively bypasses the data model. "If a lot of the good stuff is going to end up in memo fields", say the chaoticians, "why bother building an elaborate table/field structure that will atrophy over time anyway?"