h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Funny how I always thought that diabetes was either (type 1) a lack of insulin production in the pancreas or (type 2) a resistance to using the insulin produced to metabolise glucose rather than a blood vessel disease as is stated here.

Actually diabetes mellitus is a heterogeneous group of disorders that have hyperglycemia as a common feature. Diabetes is a chronic disorder of protein, fat and carbohydrat metabolism with many etiologies:
Primary Diabetes includes:
Type 1 diabetes, formerly known as insulin dependent diabtes or juvenile diabetes (which as you correctly mentioned was a deficiency of the pancreas, more specifically of the Islet cells)
Type 2 diabetes, formerly known as non-insulin dependent, or adult onset (which you also correctly said was tissue resistence to insulin; this form may have features of islet cell deficiency, espically common is a low level of beta-cell depletion).
Many genetic defects in beta cell function (MODY forms 1,2,3 are errors of HNF 4 alpha, glucokinase, and HNF 1 alpha)
Secondary diabetes has many causes infectious, drug related, other genetic disorders (like trisomy 21, Down syndrome).
However, despite the myriad of causes of diabetes, the functional losses are related to damage to the blood vessels. They are traditionally divided into microvascular and macrovascular. This damage is the result of hyperglycemia that causes irreversible advancedglycosylation end products which accumulate over time on blood vessel walls.
Diabetes is defined by hyperglycemia, but the mordibity of diabetes is defined by vascular damage. It's certainly a fine point, but by thinking of diabetes as a syndrome of sugar (as well as fat and protein) dysfunction causing vascular damage we can understand many of the common complications of the disorder.
Thanks for your feedback, if you want any further information about the other forms of diabetes just let me know. I've recently spent a lot of time in the field. It's quite interesting because many people know the two big etiologies (Type 1 and Type 2). Even physicians are having difficulty with the other etiologies. Some claim failures in therapies that would other work are do to "patient non-compliance" and are not catching rare sources. If the other etiologies were better studied I suppose we would find a higher incidence in these "rare" cases.