My experience of agile is exactly the reverse. In the last three years or so I have worked on about eight sites that use it and in all of them, there is a problem of a lack of documentation. There is also a lack of any longer term view than the next day or two, so the problem that Steve correctly highlights is exacerbated.

In the BI world I am reading blogs telling me that OLAP is a dead technology because we now have column store databases/indexes. This seems to be a part of the "Agile" approach that we have to write code in the first two weeks of any project - see http://www.agilemanifesto.org/. I think that this is merely a euphemism for "we don't like documentation, we just want to write code". Codd must turning in his grave.